Merge branch 'hotfix/3.0.4'
Fix the `.gitattributes` file
Correctly load the language files (see #5384)
Update the forum link in the referer error message (see #5389)
Remove the pixel unit from the video width and height attributes (see #5383)
Bump the version number to 3.0.5
Merge branch 'hotfix/3.0.5' into develop

Conflicts:
	system/config/constants.php
	system/docs/CHANGELOG.md
	system/modules/core/library/Contao/System.php
	system/modules/core/templates/be_referer.html5
Remove all references to `parent` in the decoupled library classes