Add CORS origins for Scratch and ScratchX

Scratch hardware extensions are written in JavaScript and loaded in
Scratch (https://scratch.mit.edu) or the experimental extension site,
ScratchX (http://scratchx.org).

This change will allow the Scratch Arduino extension to use the
Create agent to communicate directly with Arduino boards.

Author: khanning

config.ini

@@ -7,4 +7,4 @@ v = true  # show debug logging
 appName = CreateBridge
 updateUrl = http://downloads.arduino.cc/
 #updateUrl = http://localhost/
-origins = http://webide.arduino.cc:8080
+origins = http://webide.arduino.cc:8080, https://scratch.mit.edu, http://scratchx.org