Adds AsyncGraphics package with Circles app

[heestand-xyz]

• Adds new package AsyncGraphics
• Adds new app Circles powered by AsyncGraphics
• Removes old app Pixel Nodes (It's not on AppStore anymore and link was broken)
• Updates link to PixelKit

[heestand-xyz]

@terkelg Is there anything I can do to improve this PR? I would appreciate your feedback.

[heestand-xyz]

Thank you @terkelg