.NET 5 support via FsAutoComplete and Neovim 0.5 LSP client #90

As not much appears to be happening here I went ahead and configured the other F# LSP server to work with Neovim 0.5. F# with Coc isn't too bad but I feel like the future is a built-in LSP Client.

All the basic stuff works out of the box (with some key bindings of course) and was really easy to setup. FsAutoComplete already support .NET 5 which is another bonus.

Check it out at https://github.com/neovim/nvim-lspconfig/blob/master/CONFIG.md#fsautocomplete

Feedback welcome.