Refactored lsp and null ls configs

after/plugin/lsp/null-ls.lua

@@ -0,0 +1,18 @@
+local setup, null_ls = pcall(require, "null-ls")
+if not setup then
+	return
+end
+
+local formatting = null_ls.builtins.formatting
+local diagnostics = null_ls.builtins.diagnostics
+
+null_ls.setup({
+	sources = {
+		formatting.stylua,
+		diagnostics.eslint_d.with({
+			condition = function(utils)
+				return utils.root_has_file(".eslintrc.js")
+			end,
+		}),
+	},
+})