Add tree-sitter.json.

[EugeneNeuron]

This file is expected by tree-sitter CLI.
It allows to infer file types, injection-regex, etc. during tree-sitter test [1].

[1] https://tree-sitter.github.io/tree-sitter/3-syntax-highlighting#query-paths

[vantreeseba]

I'm not sure if including this in this repo itself is the intended use case.
This seems to a be a file typically used by an IDE/cli itself to define the configuration for using tree-sitter.

I know neovim treesitter puts it's own version of this somewhere and requires you to copy the query/etc files over.

That being said I don't know if there is actually an issue with including this, so I may pull it in soon, but thank you for the contribution.

[EugeneNeuron]

I don't know how IDEs or neovim treat this file. Maybe neovim puts it's own version of this because the repo itself doesn't provide it, I don't know.

I just know that:

1. it's needed for tree-sitter CLI to run highlight tests.
2. it's created by tree-sitter init.
3. it's present in all upstream official grammars (and other well-maintained as well), e.g. python, javascript.
4. it's expected by the tree-sitter: "Language configuration in grammar repositories' tree-sitter.json files" (from link above).