Add license headers and eslint rules for them

.eslintrc.js

@@ -1,3 +1,21 @@
+const copyrightTemplate = `/*
+ * Copyright 2020 Spotify AB
+ *
+ * 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.
+ */
+
+`;
+
 module.exports = {
   extends: [
     '@spotify/eslint-config-base',
@@ -9,6 +27,7 @@ module.exports = {
     'plugin:jest/recommended',
   ],
   parser: '@typescript-eslint/parser',
+  plugins: ['notice'],
   env: {
     jest: true,
   },
@@ -22,5 +41,20 @@ module.exports = {
     },
   },
   // Adding this to .eslintignore just doesn't even, let me know if you can make it work ._.
-  ignorePatterns: ['**/*_pb.js', '**/*_pb.d.ts'],
+  ignorePatterns: [
+    '**/*_pb.js',
+    '**/*_pb.d.ts',
+    '**/dist/**',
+    '**/cjs/**',
+    '**/esm/**',
+  ],
+  rules: {
+    'notice/notice': [
+      'error',
+      {
+        template: copyrightTemplate,
+        onNonMatchingHeader: 'replace',
+      },
+    ],
+  },
 };