Generate release notes from PR descriptions

[132ikl]

This PR updates the release notes script to fully generate the release notes from the PR descriptions. More details can be found here: https://hackmd.io/1ryo_LLWQPuWvzfQ8pwVUw

The script performs multiple checks on the PR to make sure we get a good generated output. PRs will be flagged with warnings or errors if something is amiss. The summary is pulled directly from the PR on GitHub, so we can make changes to the description or labels as needed.

Here's an example of some warnings and errors when something is wrong with a PR:

TODO:

• Finalize labeling scheme
• Actually generate the release notes
• Add check-prs command
• Figure out where to put PR link for multi-line summaries
• Should "Notes for plugin developers" get its own PR tag?
  • for now no, revisit this if necessary
• Integrate with create-pr.nu
• Documentation
  • Clean up Release Note Generation doc
  • Create how-to documentation
  • Reference how-to in Nushell CONTRIBUTING.md (guide for merging PRs and guide for generating release notes)
  • Update nu_scripts release notes README to link to how-to
• Add summaries and labels to v0.107.0 PRs

[132ikl]

there's still some things to figure out here, but the actual generation of release notes works and the code is ready to review for all intents and purposes

[Bahex]

Everything look goods to me 👍

Also thank you so much for this, preparing release notes will be a breeze compared to before ❤️