Animated PNG Custom Theme Icons

[pelaird]

Please add the ability to use animated PNG files for custom theme icons. For example, the "stop" icon being animated as rotating "reload" icon.

[Pesala]

@pelaird This already works. I have a couple that I use for Capture Page / Selection, and Toggle Images.

I use APNG Anime Maker to create my APNG images. (Use suffix *.PNG)