nvim: treesitter: Make PureScript use Haskell parser and queries

Turns out that the Haskell treesitter implementation can be used
for PureScript as well.

This is exactly what Helix does.
https://github.com/helix-editor/helix/pull/4242/files

nvim/.config/nvim/lua/treesitter.lua

@@ -17,5 +17,8 @@ require'nvim-treesitter.configs'.setup {
   },
 }
 
+-- Make PureScript use Haskell parser and queries.
+vim.treesitter.language.register('haskell', 'purescript')
+
 vim.keymap.set('o', '<Leader>m', ':<C-U>lua require(\'tsht\').nodes()<CR>', { noremap=false, unique=true, silent=true })
 vim.keymap.set('x', '<Leader>m', ':lua require(\'tsht\').nodes()<CR>' , { noremap=true , unique=true, silent=true })