Fork chessboard.js to fix flickering

See oakmac/chessboardjs#97

Author: raxod502

README.md

@@ -69,3 +69,9 @@ Or you can render another Markdown document:
 
 Typically the server runs on `localhost:6419` if that port is
 available.
+
+### Vendored files
+
+We vendor a forked version of `chessboard.js` from
+[here](https://github.com/raxod502/chessboardjs/blob/whales/src/chessboard.js),
+minified [online](https://javascript-minifier.com/).

app/html/play.html

@@ -19,7 +19,7 @@
       </div>
 
     <script src="https://code.jquery.com/jquery-3.3.1.min.js"></script>
-    <script src="/js/vendor/chessboard-0.3.0.min.js"></script>
+    <script src="/js/vendor/chessboard-98b2382.min.js"></script>
     <script src="https://cdnjs.cloudflare.com/ajax/libs/chess.js/0.10.2/chess.js"></script>
 
     <script src="/js/util.js"></script>