[BUILD] AppStream metadata issues

The p tags inside description should be translated, not the description tag itself.

This causes the default description to be incorrectly in French instead of English (or correct translations) and causes other problems.

Also, there is no launchable tag that is required by newer AppStream standard and some validators/parsers and the screenshot url is incorrect.

Please see the original Pull request that I created before (but closed afterwards because I was told by the developer that this upstream repository is no longer maintained).