Algunos enlaces de ayuda
https://developer.mozilla.org/en-US/Add-ons/WebExtensions
https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Your_first_WebExtension
https://github.com/mdn/webextensions-examples
https://marti1125.gitbooks.io/aprendiendo-sobre-webextensions-api/content/