nvim: Add mapping to toggle buffer diagnostics

If you want to hide buffer diagnostics for any reason, there is now a
quick mapping reachable through the usual lsp submenu: `<localleader>lo`
(I suppose the mnemonic would be 'lsp off').

It toggles them enabled and disabled and only affects the current
buffer.

nvim/.config/nvim/lua/plugins/config/lsp.lua

@@ -109,6 +109,13 @@ local function on_attach(client, bufnr)
 		"<cmd>lua vim.lsp.buf.signature_help()<cr>",
 		{ buffer = bufnr, desc = "Signature help" }
 	)
+	map("n", "<localleader>lo", function()
+		if vim.diagnostic.is_disabled(0) then
+			vim.diagnostic.enable(0)
+		else
+			vim.diagnostic.disable(0)
+		end
+	end, { buffer = bufnr, desc = "Disable buffer diagnostics" })
 
 	if vim.g.format_on_save then
 		require("lsp-setup.utils").format_on_save(client)