Code-ast

This is a small intermediate release for fixing bugs and adding a few minor feature requests.

Main changes:
- code_ast will now temporarily enforce `tree_sitter==0.21.3` during installation
- code_ast now supports pre-compiled language libraries with `tree_sitter_languages`
- Some minor dependency updates.

The first version of code_ast.

Features
The version introduces the following features:

* Introduction of AST Parsing API
* Fast AST parsing backend based on Tree-Sitter
* Full support of Tree-Sitter: Currently, all languages which are supported by Tree-Sitter can be parsed
* Auto loading: The parser definition for each language is automatically downloaded