feat request: add ft field in lsp spec

[xiaoshihou514]

Feature description

Thanks for this great one-stop solution for setting up Haskell dev environment!
This feature request is here because I have sth in my status line that checks if the attached lsp's filetype contains the current buffer's ft. It would be very nice if haskell-tools.nvim provide these so that other plugins/scripts can identify haskell-tools.nvim as a Haskell lsp.

vim.print(vim.lsp.get_active_clients()[1].config.filetype)                                                         
-- Expected: {"haskell", "cabal" ...}
-- Actual: nil

[mrcjkb]

Hey 👋

Sure, that shouldn't be hard to implement. I'll look into it later today 😊

[xiaoshihou514]

Thank you!