Add mention of Tree-Sitter WIP work

[jsmestad]

I find myself searching for @wkirschbaum's tree-sitter fork all the time so I wanted to add a link from our README for others searching for it as well.

[wkirschbaum]

Even though it is still work in progress, I believe it reached a state where it can replace elixir-mode so is probably stable enough to remove the "WIP" - the README has been updated with better instructions. It does not have some of the fancier features elixir-mode has, but also don't believe it should be in the elixir-ts-mode.

I started the assignment process and will probably submit elixir-ts-mode and heex-ts-mode to emacs master ( for release with emacs 30, unfortunately I am too late for 29 ) to hopefully provide an out of the box experience for elixir hackers in the future... until then maybe submit it to MELPA so we can modify elixir-mode to use elixir-ts-mode and heex-ts-mode as as dependency where emacs users don't have to worry too much about changing packages and see if we can make it just work or work with little effort. Once it lands in emacs core we can just update the dependency on this package to deal with it.

[jsmestad]

I think having this in MELPA today would be a great idea

[wkirschbaum]

Great :). It will be tomorrow for me, but will work on MELPA submission before caring about forward-sexp ( i think i am the only person really missing it and was also the reason why I started hacking on elixir-mode 😆 )