Add support for haskell-tng-mode

[LaurenceWarne]

Hi! This PR adds support for haskell-tng-mode. It does this by removing the hard requirement on haskell-mode and adding haskell-tng-mode to the list of modes when registering the client.

haskell-mode is currently used only in (AFAICS - I've been running it locally without haskell-mode with no issues):

• lsp-haskell--get-root -> change: aliased to lsp--suggest-project-root
• lsp-haskell--session-cabal-dir -> change: first check if haskell-cabal-find-file is bound and fall back to lsp--suggest-project-root if necessary

Thanks, let me know what you think.

[michaelpj]

This looks fine to me. I suggest just getting rid of lsp-haskell--get-root, it's just redundant. I'd be tempted to bin lsp-haskell--session-cabal-dir - we have a few of these not-really-lsp-related utility functions that IMO don't really belong here.

[LaurenceWarne]

This looks fine to me. I suggest just getting rid of lsp-haskell--get-root, it's just redundant. I'd be tempted to bin lsp-haskell--session-cabal-dir - we have a few of these not-really-lsp-related utility functions that IMO don't really belong here.

Cool, if that's ok, I've removed both of them in the last commit.

[michaelpj]

Thanks!