Add release instructions

[dcherian]

1. Update whats-new and CITATION.cff
   1. Create a new section with date in whats-new.rst
   2. Add entries in the section looking at recent commits.
   3. Create a PR to update whats-new.
   4. Add version info and release date at bottom of CITATION.cff
   5. Add the test-build tag.
   6. Make sure tests pass.
   7. Merge the PR.
2. Tag a release using the Github UI
   1. Click "Draft a new release"
   2. Add a new tag vX.Y.Z
   3. Use vX.Y.Z as name
   4. Generate release notes, and edit to make it understandable to Github users.
   5. Create the release!
3. After the tag is created, a Github Action to deploy to pypi will be triggered. Monitor to make sure this succeeds (click "Actions")
4. Wait for the conda-forge PR to show up and merge that after checking that requirements have been updated.

[dcherian]

@kthyng you should have rights to create a release. Let's try it out!

Please add a whats-new note for #397

[kthyng]

Do you want me to add this as a docs page?

[dcherian]

Sure could go under "Contributing Guide", but let's make sure its comprehensive first.

[kthyng]

The recent releases don't really have anything in the release description. Should I just copy in the stuff from "What's New"?

[dcherian]

That's annoying because it's in rst while github expects markdown. Click thee "Generate release notes" button and edit what it gives you.

Github is surfacing these things in the UI now so it's nice to add.

[kthyng]

Um this is super awesome! I just clicked through and I see this, which looks very thorough:

but when I look at the releases on github I see the following which doesn't really show anything for the past few releases:

Am I missing something?

[dcherian]

What you have is nice. Let's go with that. You could remove things that seem like trivial maintenance things, but it's not necessary

I think I was being lazy for the last ones.

[dcherian]

:clap: :clap: that worked well! https://pypi.org/project/cf-xarray/

[kthyng]

I think your instructions were good!