Update to use tree-sitter-teal for partial parsing

[FourierTransformer]

Main Changes

• Switched to using tree-sitter-teal to do parsing of any potentially valid code. The nice thing about using the tree-sitter is that it handles incomplete documents really well, and then you can extract tokens in a predictable way.
• It uses the idea of pulling out the tokens as a list and then iterating forward using Teal's symbols_in_scope (fully explained here: Update backend calls for hover, completion, and definition #22 (comment)) to handle completion, hover, go to definition, and signature help.
  • Tree-sitter solves the self problem I encountered before, by just going up the tree, I can easily determine what self refers to and use that while looking in the symbol table.
• It handles completion when the user is at a :, ., or (, and also before it.
  • Properly handles filtering functions with self by matching the original type on : or seeing if the first arg is self
  • If you're typing if foo, the language server can show all symbols that are in scope while typing foo.
• Added LSP completion item kind to the completion results (results in symbols showing up during completion)
• Shows record/enums/polymorphic information on hover
• Also show type info when hovering on bar in foo.bar
• Switched to using Markdown for the hover and function signature help. It looks a bit nicer, and when teal is more widespread will highlight correctly
• Small perf changes

Packaging Issues

• I'm using ltreesitter for loading the teal tree-sitter grammar, but it requires the tree sitter lib installed on the system as well as the teal.so from the grammar to be present.
  • Both of these make it a little hard to just luarocks install the langauge server and get things going. This should probably be required before releasing the next version

closes #6 #19 #23 #24