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.
Use the new vim.lsp.start API and LspAttach/Detach auto commands.
Drop nvim-lspconfig in the process.
LSP server specific configuration has been taken from nvim-lspconfig.