add paypal donate button

index.html

@@ -80,12 +80,21 @@
     <div class="sharing">
       <a href="https://twitter.com/share" class="twitter-share-button" data-text="Check out 2048, a game where you join numbers to score high! #2048game" data-via="gabrielecirulli">Tweet</a>
       <script>!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0],p=/^http:/.test(d.location)?'http':'https';if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src=p+'://platform.twitter.com/widgets.js';fjs.parentNode.insertBefore(js,fjs);}}(document, 'script', 'twitter-wjs');</script>
+
+      <form class="pp-donate" action="https://www.paypal.com/cgi-bin/webscr" method="post" target="_blank">
+        <input type="hidden" name="cmd" value="_s-xclick">
+        <input type="hidden" name="hosted_button_id" value="W59BD72T97DVC">
+        <button name="submit"><img src="meta/icon_PP.svg">Donate</button>
+        <img alt="" border="0" src="https://www.paypalobjects.com/en_US/i/scr/pixel.gif" width="1" height="1">
+      </form>
+
       <span class="btc-donate">
         <a href="bitcoin:1Ec6onfsQmoP9kkL3zkpB6c5sA4PVcXU2i">
-          <img src="meta/icon_bitcoin.svg">Donate
+          <img src="meta/icon_bitcoin.svg">Donate BTC
         </a>
         <span class="address"><code>1Ec6onfsQmoP9kkL3zkpB6c5sA4PVcXU2i</code></span>
       </span>
+
     </div>
   </div>