Port announcements generation to the new Hugo based website

The kde.org website will soon switch to the Hugo framework, this changes a few things but also simplify a lot of things. We don't need to put a line on the index and announcement pages anymore, the expected output is markdown instead of html/php, and the translations are handled by the website so there is no need to put i18n() call everywhere.

I wasn't able to test it locally as I wasn't sure what script allows me to download all the framework repository.

cc @dfaure

Please don't merge until websites/kde-org!14 (merged) is merged.