Catalog existing rulesets

[alexeagle]

Find whatever rulesets we can, or based on some criteria.

Assess their current state, such as:

• active
• perform releases and how often
• quality/reliablity
• who are the maintainers

This is like a conceptual merge of

• Jin's https://awesomebazel.com
• https://bazel.build/rules
• https://docs-legacy.aspect.build/stats

Note that we want to avoid overlap with the effort Bazel core team is making in https://github.com/bazelbuild/bazel-central-registry and https://registry.bazel.build - in particular we shouldn't try to map the dependencies between rulesets.