Allow Bedrock addons to register custom potion effects via Script API

Currently, Bedrock addons cannot define new status effects that behave like native potion effects (e.g., Jump Boost, Poison, Health Boost). This limits advanced addon design, especially for RPG systems, custom mobs, and custom potions.

Addons can simulate effects through scripting, but they cannot:

• Register new effect IDs

• Display them natively in the UI

• Allow /effect commands to interact with them

• Integrate with milk, beacons, or effect stacking

This makes it impossible to build systems like custom curses, health drain, corruption, frostbite, or other debuffs in a clean and consistent way.

I suggest exposing a Script API or JSON registry that allows addons to register custom effects with:

• An ID and display name

• Color and icon

• Stacking rules and max amplifier

• Tick/update callbacks

• /effect compatibility

• Milk and clear command compatibility

Example use case: a "Health Drain" effect that reduces maximum health by 1 heart per level for a duration, applied by custom mobs and potions.

This would greatly expand the creative and technical potential of Bedrock addons while keeping it sandboxed and optional.