Automate the release process somehow

[dduan]

We have been using CHANGLOG.md. I wonder if it's better to have a script that makes the releasing process better. It can

1. Prepare the patch that would be tagged
   • bump all reference to versions in docs, tec
   • generate entries in CHANGELOG.md (ideally, check for PR numbers in existing entries, if it already exists, don't generate for that PR)
2. Prepare the release
   • Tag a given commit
   • Push the tag
   • Create a draft release, posting the corresponding release note from CHANGELOG.md
   • Download the source bundles generated for the commit, and generate shasum 256 for each one, and include them as part of draft release note.

These should be 2 separate phases, maybe handled by separate scripts.