Symbolic icons for panel-plugins

This page is still a work-in-progress and currently not much more than a collection of notes!

Findings so far

Example of porting normal icons to symbolic icons
Use standard icon names as much as possible
Use the new (Gtk3>=3.14) gtk icon encoder to convert symbolic icon svgs to pngs in the sizes you need them
- Example of what sizes to encode symbolic icons to (note that 22px is excluded because 16px doesn't scale well to it.)
  - ./16×16/status/mail-unread-symbolic.symbolic.png
  - ./16×16/status/mail-unread.png
  - ./24×24/status/mail-unread-symbolic.symbolic.png
  - ./24×24/status/mail-unread.png
  - ./32×32/status/mail-unread-symbolic.symbolic.png
  - ./32×32/status/mail-unread.png
  - ./48×48/status/mail-unread-symbolic.symbolic.png
  - ./48×48/status/mail-unread.png
  - ./scalable/status/mail-unread-symbolic.svg
  - ./64×64/status/mail-unread-symbolic.symbolic.png
  - ./96×96/status/mail-unread-symbolic.symbolic.png