Bug 994280 - It would be nice to have ability to add badge over button

- Added badge support for both `ActionButton` and `ToggleButton`
- Unit Test needs to be added

**Notice** that this PR needs the platform patch attached in bug 994280 to work properly.
And [bug 1037528](https://bugzilla.mozilla.org/show_bug.cgi?id=1037528) is a probably a blocker to land this feature.