Magenta Conventional Comments per 564bff00ff

This is a tiny extension that adds a conventional comment button to GitLab file explorer comments, allowing to quickly leave a structured semantic comment during your MR reviews! The upstream version (https://gitlab.com/conventionalcomments/conventional-comments-button) does not work for self-hosted instances. This extension simply changes the manifest to run on git.magenta.dk -- as well as some other minor changes.