QuakeC grammar for [[https://github.com/tree-sitter/tree-sitter][tree-sitter]].

As the language has many dialects and extensions and is not well-defined, the grammar had to be developed in an ad-hoc way based on the dialect used by the 2021 Quake 1 rerelease ([[https://github.com/vkazanov/tree-sitter-quakec/tree/main/examples/rerelease][included]] directly for testing purposes).