Send modifier keys to VM but allow bubbling

This allows the keys to be used for developer shortcuts, but also keeps the "if any key pressed" block working (and hacked key blocks).

src/lib/vm-manager.js

@@ -23,13 +23,14 @@ class VMManager {
         // Don't capture keys intended for Blockly inputs.
         if (e.target !== document && e.target !== document.body) return;
 
-        // Don't capture browser keyboard shortcuts
-        if (e.metaKey || e.altKey || e.ctrlKey) return;
-
         this.vm.postIOData('keyboard', {
             keyCode: e.keyCode,
             isDown: true
         });
+
+        // Don't stop browser keyboard shortcuts
+        if (e.metaKey || e.altKey || e.ctrlKey) return;
+
         e.preventDefault();
     }
     onKeyUp (e) {