Add missing license file.

Author: ditman

renderers/lit/src/v0_9/tests/markdown.test.ts

@@ -1,3 +1,19 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 import { setupTestDom, teardownTestDom, asyncUpdate } from "./dom-setup.js";
 import assert from "node:assert";
 import { describe, it, before, after } from "node:test";