Version Icon troch magicp

Compatible with Firefox 51+

* Support Firefox 55+ for Android as menu item.
* Firefox beta version number is different with about:support page's one, for example "57.0" (not "57.0b1"). This is intentional behavior of JavaScript API.

NEW RELEASE
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Tab Counter Icon
Shows number of open tabs as icon.

https://addons.mozilla.org/firefox/addon/tab-counter-icon/
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