High-level release highlights

[achimnol]

Like pantsbuild, let's introduce a high-level release highlight section to each release note.
These high-level release highlights may be continuously updated, and should be:

• copied into the front-matter of the long_description of the wheel packages (displayed in pypi.org)
  • https://pypi.org/project/backend.ai/ – Currently it contains README.md only.
  • This may require modification of our setupgen pants plugin.
• linked in the notes of GitHub releases.

Examples:

• https://github.com/pantsbuild/pants/blob/main/docs/notes/2.22.x.md
• https://github.com/pantsbuild/pants/blob/main/docs/notes/2.21.x.md
  • https://github.com/pantsbuild/pants/releases/tag/release_2.21.0

To make it easier to automate copy-and-pasting of them in the release pipeline, let's add a dedicated directory (suggested: docs/release-notes/{24.03,24.09,...}.md) in this mono-repo.

(cc: @kimjmin, @YEONFEEL96)

[achimnol]

I will first make drafts for 24.03 and 24.09 releases.