Adds a label to Pull Requests that were created using AGit-Flow,
in order to prevent situations where a contributor uses AGit-Flow
to push new changes - only to realize that they did not use AGit-Flow
in the first place, and that they just opened a new PR accidentally
(that was me).
Also intended to raise general awareness about the feature. Some
additional work, such as adding a tooltip, still needs to be
done.
A small typo fix for a comment and (exclusively) formatting fixes
in the copyright header are also included.
Refs: https://codeberg.org/forgejo/forgejo/issues/2433
bf7fb89178