Update release procedure in issue template

[scpeters]

We currently document the release process in a github issue template. This PR captures changes to our release process for Ionic.

[azeey]

I've been updating #1092 with the steps I've taken to create a stable branch. For each library that doesn't already have a stable branch for the release, we need to do:

• <library name>:
  • Create a changelog PR (example)
  • New branch button on branches page (example). Make sure to set the Source to main.
  • Enable CI for stable branches :
  • Update gazebodistro:
  • Update homebrew:
  • Run the Jenkins DSL generation job
  • Create a small PR targetting the stable branch. This could be used to update build status badges (example). Don't skip this; it is important for the next step:
  • Update branch protections. Remember to include the abi-checker.
  • Make a pre-release.