added 'controllermodelready'-event

[coderofsalvation]

NOTE: I need to lint this PR (but before bothering, I would love a pre-blessing of this PR)

This adds the controllermodelready event to hand-tracking-controls, so it behaves like the others controllermodels.
I've also added a examples/showcase/multi-input-anchors demo, to see it in action:

simplescreenrecorder-2025-03-06_18.39.18.mp4

simplescreenrecorder-2025-03-06_18.38.19.mp4

NOTE: Quest 2 and Webxr-emulator was used for testing (other controllers can be added in similar fashion)

Its wearable-component gives others a huge headstart, without having to worry about:

• controller-models (not) wiping/re-attaching their children after a controller-switch
• anchoring objects to specific legacy.future controllers
• the tricky when & why behind model-loaded, controllersupdated-, controllermodelready-, and controllerconnected-events.

[dmarcos]

This is a bit too specific to be part of the showcase that should be more like self-contained mini-apps

[dmarcos]

We have a watch demo. What's missing there? https://github.com/aframevr/aframe/tree/master/examples/mixed-reality/watch

[coderofsalvation]

I'm separating concerns by postponing the demo/showcase.
So this PR is now just adressing the missing event of hand-tracking-controls.

The hand-attached-menu showcase (as discussed on discord) needs some ripening (stopwatch e.g.).
I have a hunch that the wearable-component might be working around a timing-bug (which might be better to fix in AFRAME itself).
There's no hurry..slow-cooked demonstrations are better than overcooked fastfood.

[dmarcos]

Thanks!