Add haskell-language-server as lsp for cabal files

https://haskell-language-server.readthedocs.io/en/latest/features.html#cabal-parse-errors-and-warnings

languages.toml

@@ -2698,6 +2698,7 @@ file-types = [ "cabal" ]
 roots = ["cabal.project", "Setup.hs"]
 indent = { tab-width = 2, unit = "  " }
 comment-token = "--"
+language-servers = [ "haskell-language-server" ]
 
 [[language]]
 name = "hurl"