[WIP] nushell grammar for tree-sitter

• Ability to serve as a parser for a repl
• Ability to work in editors that support tree-sitter (hx, nvim, others)
• Ability to work in rust
• Fast
• Ability to be utilized for syntax highlighting
• ...

• for neovim users, please have a look at installation/neovim.md
• for helix users, please have a look at installation/helix.md

see instructions