let specify the full 'path' for FontAwesome fonts

[manuel-rubio]

Because FontAwesome is using different prefixes (https://fontawesome.com/how-to-use/on-the-web/referencing-icons/basic-use): fas, fab, far, fad and fal; I've made an addition to the specification for tidbit and widgets to let us use full_icon and specify, i.e. fab fa-google-play