exoscheme-ts-mode: Create a tree sitter version

[jamesaorson]

• Create a new file exoscheme-ts-mode.el in the root
• Reference the emacs-tree-sitter/tree-sitter-langs repo to understand how grammars are built. Racket has a grammar here. Ours can probably start as a subset of that, then be changed as needed.
  1. Try racket’s grammar, unedited, as your first test. Just copy the grammar for use for scheme.
  2. Strip it down as needed for Scheme.
  3. Currently we support guile specifically, but we should support all of the popular schemes. This means supporting not only #:keyword but also :keyword, etc.
• Reference c3-ts-mode for much of what you do.