Add haskell-ts-mode to master?

[pranshu sharma]

With tree-sitter, I was able to make a major mode that provided
indentation, font lock and navigation.  Over the last month, I've been
working on it and I can finally say it is fully ready.  I tested the
indent on large haskell programs, such as darcs and ghc, and it was
good, and it did not change the output (since indent matters in haskell
execution).

I'm willing to upstream this to master, as it would be good if emacs had
an inbuilt major mode for haskell.