nvim: Only start ltex LSP if spellchecking enabled

Since ltex-lsp eats quite a lot of resources and takes a while to start
up we don't always want it enabled for every prose file. This commit
ensures that it only starts up when spellchecking is enabled for a
buffer (through the custom user command `SpellToggle`).

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

@@ -20,7 +20,7 @@ local servers = {
 	eslint = {},
 	gopls = {},
 	julials = {},
-	ltex = {},
+	ltex = { autostart = false },
 	lua_ls = {
 		settings = {
 			Lua = {
@@ -201,3 +201,23 @@ if require("core.util").is_available("arduino") then
 		on_new_config = require("arduino").on_new_config,
 	})
 end
+
+vim.api.nvim_create_autocmd("User", {
+	pattern = "SpellEnable",
+	callback = function()
+		lspconfig.ltex.setup({
+			on_attach = function(client, bufnr)
+				on_attach(client, bufnr)
+				if require("core.util").is_available("ltex_extra") then
+					require("ltex_extra").setup()
+				end
+			end,
+			settings = {
+				ltex = {
+					language = vim.opt.spelllang:get(),
+				},
+			},
+		})
+		vim.cmd("LspStart ltex")
+	end,
+})