Add tag queries

[rewinfrey]

Based on https://github.com/mitchellh/tree-sitter-proto/pull/3, and adds tag queries used to help extract symbol data from parse trees generated from tree-sitter-proto. The symbols matched via these queries are used to populate symbol data used for code navigation and some aspects of code search on github.com.

Currently adding this to my personal fork, but ideally we'd love to have these changes upstreamed to the fork parent.

[mkatychev]

@rewinfrey do you mind submitting this to https://github.com/treywood/tree-sitter-proto ? That seems to be the defacto successor fork of this project since it got accepted into https://github.com/nvim-treesitter/nvim-treesitter/pull/5185/files