Specify freerange fork in package.json

To avoid the missing release branch error we see locally.

I think we see the error because the scratchfoundation fork of this repo
does not have an experience-cs branch.

package.json

@@ -7,7 +7,7 @@
   "homepage": "https://github.com/scratchfoundation/scratch-gui#readme",
   "repository": {
     "type": "git",
-    "url": "https://github.com/scratchfoundation/scratch-gui.git"
+    "url": "https://github.com/freerange/scratch-gui.git"
   },
   "private": true,
   "publishConfig": {