Let users make their own themes for Status

[du82]

Enable users to make UI themes for Status that can be obtained/purchased with SNT through a screen similar to the one used for stickers.

This could open up many possibilities for customization of the app's colors and style, while opening up new use cases for SNT and creators who want to earn on the app but don't have the skills in art for sticker design.

Example:

• User installs a theme for Chinese New Year that changes the icons and colors of the app to fit the occasion.
• User installs a theme that makes the app more accessible by increasing font size and making the colors greyscale.