fixing ontouchend check to account for multiple touches

Author: Lauren McCarthy

lib/p5.js

@@ -3458,7 +3458,9 @@ amdclean['inputtouch'] = function (require, core) {
   };
   p5.prototype.ontouchend = function (e) {
     this._updateTouchCoords(e);
-    this._setProperty('touchIsDown', false);
+    if (this.touches.length === 0) {
+      this._setProperty('touchIsDown', false);
+    }
     var context = this._isGlobal ? window : this;
     var executeDefault;
     if (typeof context.touchEnded === 'function') {