Version 1.4

Fifth submit to AMO

Embeds highlight.js 8.3 (instead of 8.2).

Extends background color from highlighted code block do body HTML element. There's also a preference to disable this behavior.

Version 1.3

Fourth submit to AMO

Improves the interface: button reacts tab-wise, panel looks/reacts better.
Brings French localization.
Unit tests appeared.

Version 1.2

Third submission to AMO.
Replaced by v1.3 before review by Mozilla editors.

Replaced data/highlightjs/highlightjs.pack.js (and support for 92 languages) with data/highlightjs/highlightjs.min.js (supports 22 languages).

Version 1.1

Second submission for approval on AMO.
Rejected because highlight.js code as it is embedded is allegedly too difficult to match to an official source.

Since v1.0, innerHTML has been removed from code. The button icon has been changed to better fit to Australis style.

Version 1.0

First submission to AMO.

It was meant to be first release, but it was rejected because of the use of innerHTML to modify the page, which is generally considered as unsafe.
There should be no advantage to use this version, use later versions instead.