Better JSON UI

Currently, Minecraft Bedrock Edition allows creators to design custom interfaces using JSON UI, but the system is limited to mostly visual customization and lacks access to dynamic game data and logic.

This makes it difficult to create fully custom HUDs, menus, and interactive UI systems using only resource packs. While creators can design UI appearance, they cannot connect it to gameplay without using behavior packs or Script API.

Suggested improvements:
- Allow JSON UI to access dynamic game data such as player stats (health, hunger, armor, XP), max values, effects, and scoreboard values
- Provide built-in binding variables (e.g. #player_health, #player_xp, etc.)
- Allow UI elements to automatically update when bound values change
- Add support for simple logic (conditions, comparisons, basic math)
- Improve support for custom HUD layers to replace or extend vanilla UI

Benefits:
- Enables fully resource-pack-based UI systems
- Allows advanced HUDs, menus, and overlays
- Reduces reliance on scripting
- Makes UI creation more accessible
- Expands Bedrock’s creative potential

This would turn JSON UI into a complete UI framework, not just a visual tool.