I uploaded [your extension](https://chrome.google.com/webstore/detail/securelogin/abpigncghjblhknbbannlhmgjpjpbajj) to the [extension compatibility checker](https://www.extensiontest.com) and it [seems to work](https://www.extensiontest.com/test/d4df33c0-9ebb-11e7-9435-716f0ae708e2).  Please [upload it to AMO as a zip](https://addons.mozilla.org/en-US/developers/addon/submit/distribution). You can test it in `about:debugging` in Firefox. Check out [browser support](https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Browser_support_for_JavaScript_APIs) and [web-ext](https://developer.mozilla.org/en-US/Add-ons/WebExtensions/web-ext_command_reference).