chore: set license headers

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

src/github.ts

@@ -1,3 +1,19 @@
+/**
+ * Copyright 2023 actions-toolkit authors
+ *
+ * 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
+ *
+ *      http://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 {GitHub as Octokit} from '@actions/github/lib/utils';
 import * as github from '@actions/github';
 import {components as OctoOpenApiTypes} from '@octokit/openapi-types';