contrib: Add script to bump stable releases

[joestringer]

Add a script to create a new commit bumping the README and github
actions for newly released versions.

Usage:

$ git fetch origin
$ git checkout -b pr/bump-readme-$(date --rfc-3339=date) origin/master
$ ./contrib/release/bump-readme
$ git push
<open PR>

Used to create #10710.

[coveralls]

Coverage increased (+0.002%) to 45.512% when pulling bd785d0 on joestringer:submit/bump-release-script into c08e72a on cilium:master.

[christarazi]

I usually like to add set -euo pipefail for bash scripts. It would be great if we can add this to the docs as well. Otherwise, nice!

[joestringer]

Ah, good point, I was assuming that these are set in the included common/lib scripts and that those settings would propagate out to this script, which I think is true but worth double-checking.

Agree on the docs, question will be whether we move towards retiring the docs for generating releases and roll this into the github issue template for releases.

Or for that matter if we just avoid using this script manually and script up a github action to invoke it automatically..

[christarazi]

I quickly glanced at the "usage" section of the script and thought that could go in the docs. But it seems simple enough after a second look, so probably not worth doing. Eventually a GitHub action is probably the most fitting for this kind of thing. 👍

[aanm]

@christarazi @joestringer is this good to be merged besides my nits?

[christarazi]

@aanm Good to go for me.

[joestringer]

Moved, and updated the issue template for releases.