Release note (candidate) generation of Google Cloud BOM / Libraries BOM

@chingor13

**Is your feature request related to a problem? Please describe.**

A feature request.

**Describe the solution you'd like**

I'm thinking to create release note of the Libraries BOM through "DevRel Release Notes Manager". Given a release of Libraries BOM, it would be great if I can get the list of changes in the Google Cloud client libraries that occurred since the last release of the Libraries BOM.

Note that the Libraries BOM imports the Google Cloud BOM. Therefore the notable changes in the client libraries between Google Cloud BOM releases works very well.

**Describe alternatives you've considered**

I can manually ask the Google library developers for new features they implemented since last release.

**Additional context**

https://cloud.google.com/ai-hub/docs/release-notes is an example page generated by "DevRel Release Notes Manager".

In general, a good release note has noteworthy user-facing changes and a brief overview of changes, with links to more information.

My current thinking is that the automation would generate candidates for release notes. A human (the releaser of the Libraries BOM) still need to adjust links and words in a customer friendly manner. (If you think automation is not a good idea, let me know your thought.)