Verify features that are made "HTTPS-only" should be available on .onion sites as well

Firefox 49 is adding an isSecureContext attribute (https://developer.mozilla.org/en-US/docs/Web/API/Window/isSecureContext) we should make sure it returns true on .onion sites as well.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information