Add support for circular gradients, prepare shaders to allow setting center.

Add simple radial gradient support, fix lint warnings.

Allow configuring where colour stops occur.

Add support for colour stops, equally spaced.

10 stops should be generous!

Add angular linear gradient support!

Add basic support for linear gradients!

Implement background-size!

Fix parsing of background-image, attempt to fix image rendering.

Build texturing infrastructure & implement background-color!

Parse background-color for image data.

Add support for background-clip & prepare for multilayered backgrounds!