add release script

[zachschuermann]

add release script to start automating our releases with cargo-release and git-cliff. the main release script is ./release.sh with rather straightforward usage. we use cargo-release to handle some of the Cargo.toml updates and trigger git-cliff, but otherwise the script just manually uses cargo/git to publish the release and tag it

the release flow will be the following:

1. from an up-to-date main branch, checkout a new release branch (like prepare 0.x.y)
2. run ./release 0.x.y to do the 'prepare' phase of generating a changelog, updating readme etc.
   a. the tool will validate that you're on a release branch, generate the changelog, and make a commit and (optionally) open a PR (cargo-release is used to update the versions correctly and git-cliff is used as a hook in cargo-release to generate the changelog)
   b. then the only main action is just making minor CHANGELOG changes and updating + merging the PR
3. merge the 'prepare' PR
4. from main branch with prepare branch merged, run: ./release.sh
   a. the tool will publish any unpublished version (e.g. if 0.6.0 is latest on crates.io and the prepare PR bumps to 0.6.1 then the tool will do the release for delta_kernel and delta_kernel_derive, add a git tag, and push the tag)
   b. NOTE: this is currently done manually but could leverage cargo-release in the future

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.46%. Comparing base (fafc776) to head (d2c3d23).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #636   +/-   ##
=======================================
  Coverage   83.45%   83.46%           
=======================================
  Files          75       75           
  Lines       16919    16919           
  Branches    16919    16919           
=======================================
+ Hits        14120    14121    +1     
+ Misses       2145     2143    -2     
- Partials      654      655    +1     

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[nicklan]

Do we need to update the PR template to say to include the various feat, fix, doc etc things?

[zachschuermann]

FYI this is a bit of a gross hack - I think we can fix this in the future with a hook that just does some regex prior to this