Paints support for chatterino7

[williambulin]

Pull request checklist:

• Color gradients
• Angle rotation
• Username color blending
• Shadows
• API calls

Platforms tested:

• Windows
• macOS
• Linux (tested with GCC 11.2.0 on arch x64 btw)

Screenshots

Notes

• There's no obvious way to do shadows with Qt that I could find for the text rendering method Chatterino uses.
• We still need to do an API call to associate a user with a paint.
• Paints are also functionnal to mentionned users in chat right now.

Additional notes

• SevenTVGradient objects are meant to be cached as shown in the example, however you cannot cache the QPen objects since they are generated with the user color for blending (you could cache the ones that don't require color blending however, or cache it per user or per chat color).
• Rendering the text twice with the gradient on top to blend with the original username unfortunately looks terrible and therefore isn't really an option, on top of having potential performance concerns.

[TroyKomodo]

Any news on this PR?

[AnatoleAM]

This was picked up at #89