Added Pop OS icon.

[olivercalder]

Added Pop!_OS logo to the icons directories. The source image was the official logo svg from /usr/share/icons/pop-os-branding/pop_icon.svg.

Conversion process:

1. Opened existing circular logo in gimp (in my case, used os_chrome.png) and hid it
2. Imported pop_icon.svg into gimp with size of 4000x4000 px
3. Scaled canvas to fit layers (the larger being 4000x4000)
4. Used wand tool to select body segments of the image, then filled with #ffffff
5. Scaled pop_icon.svg layer to 164x164 px (aligns nicely with the os_chrome.png circle)
6. Scaled canvas to fit layers (the larger now being 256x256 px)
7. Edited transparency of pop_icon.svg layer to 75.0
8. Exported canvas (with os_chrome.png layer hidden) as os_pop.png