Create GitHub releases for tags

[kaste]

I would like to do this similar to how we create PR's. I especially like that we don't create them by using the API but just open the typical webpage but prefilled with some values.

For releases this is generally the URL we need to call: https://github.com/timbrel/GitSavvy/releases/new?body=Hi&title=ho&tag=4.56.0&target=master

If we just pushed a tag then we omit the target. If not providing a tag(-name) and the target will create that tag (but then unannotated, light variant I dislike) on the current master tip.

I would prefer just allowing to make releases for pushed tags. (a) we then have probably annotated tags, (b) it is clear what the release refers to. T.i. we avoid the ambiguity of if we had pushed "master" yet.