Reference to `clang.cindex`?

[EricCousineau-TRI]

Is it possible have a documented reference to clang.cindex? https://github.com/llvm/llvm-project/blob/6792069a3fdb412d06dd3cc42a6181c6fb7db860/clang/bindings/python/clang/cindex.py

It's basically some simple Python bindings (using cdll) to interface with libclang: https://github.com/llvm/llvm-project/blob/6792069a3fdb412d06dd3cc42a6181c6fb7db860/clang/bindings/python/clang/cindex.py#L4171-L4178

Perhaps it'd be useful to have a brief comparison of why CastXML is better than libclang? (and also some places where libclang has more info than CastXML, like templates, comments, etc.?)

Relates:

• https://github.com/RobotLocomotion/drake/issues/13670
• https://github.com/CastXML/CastXML/issues/152
• https://github.com/CastXML/CastXML/issues/171
• https://github.com/CastXML/pygccxml/issues/122

(I wanted to post this in CastXML, but I dunno if it's the right place...)