Add support for Dart

[jayu]

As requested in #7 - support for Dart should be added to CodeQue.

It could be done by integrating tree-sitter-dart parser, but this parser has suboptimal grammar definition with ~3k lines of code, while JS grammar has ~1.2k lines of code.

This would impact the size of nodes mapping and WASM file and perhaps parsing speed.

It's worth doing a PoC on parser speed before investing time for integrating it with CodeQue.

Unfortunately looks like there are no other maintained Dart parsers that can be called from JS