Set www prefix for fillMurray and fillCage

[menzow]

Due to a configuration error on fillMurray.com and fillCage.com domains https requests without a www. prefix get downgraded to http. For security reasons Sketch drops any non https request which is not handled by the plugin. To fix this behaviour I added a www. prefix, which are not downgraded when connected to directly. Handling dropped request should be fixed in a future update