Autoformat all markdown files in webdev (#1718)

Author: elliette

CONTRIBUTING.md

@@ -2,6 +2,7 @@ Want to contribute? Great! First, read this page (including the small print at
 the end).
 
 ### Before you contribute
+
 Before we can use your code, you must sign the
 [Google Individual Contributor License Agreement](https://cla.developers.google.com/about/google-individual)
 (CLA), which you can do online. The CLA is necessary mainly because you own the
@@ -18,16 +19,21 @@ possibly guide you. Coordinating up front makes it much easier to avoid
 frustration later on.
 
 ### Code reviews
+
 All submissions, including submissions by project members, require review.
 
 ### File headers
+
 All files in the project must start with the following header.
 
-    // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
-    // for details. All rights reserved. Use of this source code is governed by a
-    // BSD-style license that can be found in the LICENSE file.
+```
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+```
 
 ### The small print
+
 Contributions made by corporations are covered by a different agreement than the
 one above, the
 [Software Grant and Corporate Contributor License Agreement](https://developers.google.com/open-source/cla/corporate).

README.md

@@ -2,14 +2,15 @@
 
 ## dwds [![Pub Package](https://img.shields.io/pub/v/dwds.svg)](https://pub.dev/packages/dwds)
 
-* Package: https://pub.dev/packages/dwds
-* [Source code](dwds)
+- Package: https://pub.dev/packages/dwds
+- [Source code](dwds)
 
-A service that proxies between the Chrome debug protocol and the Dart VM service protocol.
+A service that proxies between the Chrome debug protocol and the Dart VM service
+protocol.
 
 ## webdev [![Pub Package](https://img.shields.io/pub/v/webdev.svg)](https://pub.dev/packages/webdev)
 
-* Package: https://pub.dev/packages/webdev
-* [Source code](webdev)
+- Package: https://pub.dev/packages/webdev
+- [Source code](webdev)
 
 A command-line tool for developing and deploying web applications with Dart.