docs: added prettier config

docs/prettier.config.js

@@ -0,0 +1,21 @@
+/*
+ * 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.
+ */
+
+// Use Object.assign since we haven't configured eslint for ... support in here
+module.exports = Object.assign({}, require('@spotify/prettier-config'), {
+  proseWrap: 'always',
+  printWidth: 80,
+});