Make it easier for people to follow Refined GitHub releases

Description

The welcome issue has this wording in the "Updates" section, but now the "Watch" button is no longer in the header.

Any way to make it easier? https://github.com/refined-github/refined-github/issues/6090#issuecomment-1548454188 would be great, but it requires a token, which a new users doesn't have yet.

Maybe we can:

1. Fetch the form from https://github.com/refined-github/refined-github
2. Display it inline, as is

Example URLs

https://github.com/refined-github/refined-github/issues/3543

Alternatively:

1. Implement https://github.com/refined-github/refined-github/issues/6090#issuecomment-1548454188
2. Add link to our releases page

I think it's the most straightforward way. It also shows users what to expect from subscribing.

I guess is would be useful to add version notes https://addons.mozilla.org/en-US/firefox/addon/refined-github-/versions/

Firefox shows it at "available updates" page.