Update tweet value on image update

static/canvas.js

@@ -88,6 +88,8 @@ let draw = function() {
       ctx.font = fontSize + 'pt ' + font;
       ctx.fillStyle = fgColor;
       ctx.fillText(fillText, width * 0.08, height * 0.2 + fontSize * 1.4);
+
+      // Update download button
       document.querySelector('#save-image').href = canvas.toDataURL();
     }, false);
   });
@@ -101,6 +103,9 @@ let draw = function() {
 		       + '&icon=' + encodeURIComponent(icon)
 		       + '&signature=' + encodeURIComponent(signature)
 		       + window.location.hash);
+
+  // Update tweet button
+  document.getElementById('tweet-button').href = 'https://twitter.com/intent/tweet?text=Soutenez La Quadrature du Net ! ' + encodeURIComponent(decodeURIComponent(window.location.href));
 }
 
 let bgColorElems = document.querySelectorAll('.colorpicker input[type="radio"], #step3 input[type="radio"], #step4 input[type="radio"]');