Use a better link to release notes

[hobofan]

Background / prior discussions: #49, #37 (comment), bazelbuild/bazel-central-registry#357

TLDR: We are using a link based on the assumption that the release tag has the format v{VERSION}, which is true for a big percentage of packages, but not 100% reliable

Ideas and suggestions on how to achieve this are welcome!

[hobofan]

As discussed at BazelCon, it's probably viable to call the Github API from the frontend to at least determine the module version format

[alexeagle]

Yeah the tag column on https://bazel-contrib.github.io/bazel-catalog/ shows the data we want I think, and it requests https://img.shields.io/github/v/tag/seh/rules_kustomize. But I think shields.io has a backend server that talks to github API, not done from the web client.

I'm imagining a really simple solution here: first do #94 to render the latest tag badge, then we can edit the DOM to copy from the node created by the svg response and use that to create the release notes link.