Add a rule to Danger to check that translation files are not modified by developers.

docs/danger.md

@@ -28,6 +28,7 @@ Here are the checks that Danger does so far:
 - PR with change on layout should include screenshot in the description
 - PR which adds png file warn about the usage of vector drawables
 - non draft PR should have a reviewer
+- files containing translations are not modified by developers
 
 ### Quality check
 

tools/danger/dangerfile.js

@@ -118,3 +118,10 @@ if (hasPngs) {
 if (github.requested_reviewers.users.length == 0 && !pr.draft) {
     warn("Please add a reviewer to your PR.")
 }
+
+// Check that translations have not been modified by developers
+if (user != "RiotTranslateBot") {
+   if (editedFiles.some(file => file.endsWith("strings.xml") && !file.endsWith("values/strings.xml"))) {
+       fail("Some translation files have been edited. Only user `RiotTranslateBot` (i.e. translations coming from Weblate) is allowed to do that.\nPlease read more about translations management [in the doc](https://github.com/vector-im/element-android/blob/develop/CONTRIBUTING.md#internationalisation).")
+   }
+}