* docs: update composer support links
* docs: update link from wiki to docs for github issue template
* docs: update link pointing to wiki to point to new documentation
* docs: replace wiki links by documentation links in README and
CONTRIBUTING files
The composer file currently lacks a lot of details, especially the
"name" and "description", but also "require-dev" and "suggest" info.
This commit adds many more details to the composer file and updates
composer.lock for this repository. Technically the project is ready
to be shipped as composer package.