Feature request: Add Ada support

[geewiz]

I'd like to request language support for Ada (.ads, .adb) in CodeGraph.

• Tree-sitter reference implementation: https://github.com/briot/tree-sitter-ada
• Official Ada Language Reference: http://www.ada-auth.org/arm.html

Thanks for your work on Codegraph! I already use it with other languages like Ruby, and would love to see my Ada projects benefit from it, too.