[fusion-plugin-service-worker#144] Service worker should unregister itself on js uncaught exception

[chrisdothtml]

This issue was migrated from fusionjs/fusion-plugin-service-worker#144 and was originally reported by @cdlewis.

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I think it would be helpful to have the service worker attempt to unregister itself if there's a JS error. Helps stop people from shooting themselves in the foot. I'm open to taking this assuming it's possible / you agree it would be helpful.