We missed setting this and it gives an error like below when using
HLS and rust-analyzer.
```bash
LSP[rust-analyzer]: Error SERVER_REQUEST_HANDLER_ERROR: "/usr/local/share/nvim/runtime/lua/vim/lsp/_watchfiles.lua:199: attempt to index field 'capabilities' (a nil value)"
```
This reverts commit 34a5bbdacb.
HLS complains a lot (forgot the error) when trying to edit cabal files
making it almost unusable. It was nice to not require a separate plugin
for formatting cabal files, but, since this is not usable, disable it.
This allows us to have all the language server configuration in one
place and only import relevant LSP server configuration to pass to
vim.lsp.start in after/ftplugin.
While at it, we also enable deno support.
Sanchayan Maity