[FR] Add Display Keyframes for Fine-Grained Animation Control #305

Benefits to Users:

• Users gain precise control over each property during animation
• Users can easily modify a single property, for example text, to simulate a typewriter effect without needing to create multiple variants (assuming in this example variant-bound text displays are implemented)
• Allows users to interpolate individual properties, though it may come with a performance cost

Interpolation Options

• Enum, boolean, and string properties behave like command keyframes, meaning they cannot be interpolated
• For other properties, we would have two options:
  • Support Blockbench interpolation:
    • This allows users to interpolate properties like shadow radius using a custom animation curve, though it can affect performance due to NBT changes occurring each tick (I can share profiling data if you'd like an estimate of how this impacts performance in plugin mode)
    • Users can still opt for step keyframes if they wish to conserve resources
  • Treat them like command keyframes:
    • Users wanting to simulate interpolation would need to manually create multiple keyframes close together, which could support the argument for enabling interpolation in the first option

Maybe bone node display keyframes could include an option in each keyframe menu to specify whether the changes should also apply to all of its child nodes