[Documentation] Move all wiki pages into the repo and make it pretty (#2494)

docs/08_Format_API/01_How_to_create_a_new_format.md

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+Create a new file in the `formats/` folder (see [Folder structure](../04_For_Developers/03_Folder_structure.md)).
+
+The file must be named according to following specification:
+
+* It starts with the type
+* The file name must end with 'Format'
+* The file type must be PHP, written in small letters (seriously!) ".php"
+
+**Examples:**
+
+Type | Filename
+-----|---------
+Atom | AtomFormat.php
+Html | HtmlFormat.php
+
+The file must start with the PHP tags and end with an empty line. The closing tag `?>` is [omitted](http://php.net/basic-syntax.instruction-separation).
+
+Example:
+
+```PHP
+<?PHP
+    // PHP code here
+// This line is empty (just imagine it!)
+```

docs/08_Format_API/02_FormatInterface.md

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+The `FormatInterface`interface defines functions that need to be implemented by all formats:
+
+* [display](#the-display-function)
+* [stringify](#the-stringify-function)
+* [setItems](#the-setitems-function)
+* [getItems](#the-getitems-function)
+* [setCharset](#the-setcharset-function)
+* [getCharset](#the-getcharset-function)
+* [setExtraInfos](#the-setextrainfos-function)
+* [getExtraInfos](#the-getextrainfos-function)
+* [getMimeType](#the-getmimetype-function)
+
+Find a [template](#template) at the end of this file
+
+# Functions
+
+## The `display` function
+
+The `display` function shows the contents to the user and must return the object instance.
+
+```PHP
+display(): self
+```
+
+## The `stringify` function
+
+The `stringify` function returns the items received by [`setItems`](#the-setitem-function) as string.
+
+```PHP
+stringify(): string
+```
+
+## The `setItems` function
+
+The `setItems` function receives an array of items generated by the bridge and must return the object instance. Each item represents an entry in the feed. For more information refer to the [collectData](../05_Bridge_API/02_BridgeAbstract.md#collectdata) function.
+
+```PHP
+setItems(array $items): self
+```
+
+## The `getItems` function
+
+The `getItems` function returns the items previously set by the [`setItems`](#the-setitems-function) function. If no items where set previously this function returns an error.
+
+```PHP
+getItems(): array
+```
+
+## The `setCharset` function
+
+The `setCharset` function receives the character set value as string and returns the object instance.
+
+```PHP
+setCharset(string): self
+```
+
+## The `getCharset` function
+
+The `getCharset` function returns the character set value.
+
+```PHP
+getCharset(): string
+```
+
+## The `setExtraInfos` function
+
+The `setExtraInfos` function receives an array of elements with additional information to generate format outputs and must return the object instance.
+
+```PHP
+setExtraInfos(array $infos): self
+```
+
+Currently supported information are:
+
+Name | Description
+-----|------------
+`name` | Defines the name as generated by the bridge
+`uri` | Defines the URI of the feed as generated by the bridge
+
+## The `getExtraInfos` function
+
+The `getExtraInfos` function returns the information previously set via the [`setExtraInfos`](#the-setextrainfos-function) function.
+
+```PHP
+getExtraInfos(): array
+```
+
+## The `getMimeType` function
+
+The `getMimeType` function returns the expected [MIME type](https://en.wikipedia.org/wiki/Media_type#Common_examples) of the format's output.
+
+```PHP
+getMimeType(): string
+```
+
+# Template
+
+This is a bare minimum template for a format:
+
+```PHP
+<?php
+class MyTypeFormat implements FormatInterface {
+    private $items;
+    private $charset;
+    private $extraInfos;
+
+    public function stringify(){
+        // Implement your code here
+        return ''; // Return items as string
+    }
+
+    public function display(){
+        // Implement your code here
+        echo $this->stringify();
+        return $this;
+    }
+
+    public function setItems(array $items){
+        $this->items = $items;
+        return $this;
+    }
+
+    public function getItems(){
+        return $this->items;
+    }
+
+    public function setCharset($charset){
+        $this->charset = $charset;
+        return $this;
+    }
+
+    public function getCharset(){
+        return $this->charset;
+    }
+
+    public function setExtraInfos(array $infos){
+        $this->extraInfos = $infos;
+        return $this;
+    }
+
+    public function getExtraInfos(){
+        return $this->extraInfos;
+    }
+}
+// Imaginary empty line!
+```

docs/08_Format_API/03_FormatAbstract.md

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+The `FormatAbstract` class implements the [`FormatInterface`](../08_Format_API/02_FormatInterface.md) interface with basic functional behavior and adds common helper functions for new formats:
+
+* [setContentType](#the-setcontenttype-function)
+* [callContentType](#the-callcontenttype-function)
+* [sanitizeHtml](#the-sanitizehtml-function)
+* [array_trim](#the-array_trim-function)
+
+# Functions
+
+## The `setContentType` function
+
+The `setContentType` function receives a string defining the content type for the HTML header and must return the object instance.
+
+```PHP
+setContentType(string): self
+```
+
+## The `callContentType` function
+
+The `callContentType` function applies the content type to the header data and must return the object instance.
+
+```PHP
+callContentType(): self
+```
+
+## The `sanitizeHtml` function
+
+The `sanitizeHtml` function receives an HTML formatted string and returns the string with disabled `<script>`, `<iframe>` and `<link>` tags.
+
+```PHP
+sanitizeHtml(string $html): string
+```
+
+## The `array_trim` function
+
+The `array_trim` function receives an array of strings and returns the same array with all elements trimmed (like using the `trim` function on all elements)
+
+```PHP
+array_trim(array $elements): array
+```

docs/08_Format_API/index.md

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+A _Format_ is an class that allows **RSS-Bridge** to turn items from a bridge into an RSS-feed format. It is developed in a PHP file located in the `formats/` folder (see [Folder structure](../04_For_Developers/03_Folder_structure.md)) and either implements the [FormatInterface](../08_Format_API/02_FormatInterface.md) interface or extends the [FormatAbstract](../08_Format_API/03_FormatAbstract.md) class.
+
+For more information about how to create a new _Format_, read [How to create a new Format?](./01_How_to_create_a_new_format.md)