Describe the PR

• This PR provides basic info and pointers for usage and implementation of symbol tables and type resolution
• The documentation is probably not comprehensive, but I hope it's enough to show what is available and possible with PMD and maybe trigger follow up questions/discussions.
• Once such follow-up questions are there, we can improve/extend the documentation.

Related issues

• Fixes [doc] Document TypeRes API and Symbols API #4319

Ready?

• Added unit tests for fixed bug/feature
• Passing all unit tests
• Complete build ./mvnw clean verify passes (checked automatically by github actions)
• Added (in-code) documentation (if needed)