Improve themeing support

[AEAEAEAE4343]

• [ ] Allow for animations
  • [ ] Maybe add an option for timers?
  • [ ] How would we present this in a config file?
  • [ ] Maybe multiple timers at different intervals for different concurrent animation speeds?
• [ ] Add stretch option for each resource usable in ImageRenderer
• [x] ~~Improve Luna's screenshots~~ Add XP visual style renderer
• [ ] Implement Quick Launch rendering
• [ ] Add layout options (constraints, padding, margin etc.)
• [ ] Preview theme in the config menu

[Craftplacer]

I would suggest adding layout metrics too (padding, margin, sizes, size constraints, etc.) for more flexible designs.