WebXRManager: Fix hand joints not being initialized when hand connected.

[DevPika]

Fixed #24826

Description

WebXRController did not initialize the hand joints Object when hand first starts getting tracked ("connected" event). This led hand.joints being {} when accessed in the connected Event Listener. This MR fixes it by adding the initialization code to controller connect event and calling it from WebXRManager.

[mrdoob]

Lovely fix!

Shouldn't it be _getHandJoint though? Or do you think it should be a public method?

[DevPika]

Thank you for your comment! Yes, I think this method is quite specific to the class and need not be a public method, so _getHandJoint would be ideal. I will make a commit for these changes soon.

Longer note:
I was a bit confused by the conventions while comparing WebXRManager and WebXRController. WebXRManager has a public API with a few functions detailed in the docs. But some of the other functions that were not present in the docs (so they can be considered private?) also follow the same convention and should be accessible as a public method, for example:
this.getBaseLayer or this.getFrame
WebXRManager also declares all of its member methods inside the contructor which is different from the WebXRController

The WebXRController class doesn't have a doc page yet, so would that mean all of its methods are considered internal, and only need to be accessed through WebXRManager?

Sorry, I might be confusing missing documentation and intention of some methods to be available publicly.

[DevPika]

I have made the method private and updated the built module file in the Glitch example too.

[DevPika]

I am unsure if I need to mark this as ready to review on my end as this is my first MR to the repo. I don't expect to make any other changes in this MR, so I guess this means it is ready for a review? I made some changes as per suggestions from @mrdoob above, thanks for the quick feedback!

[DevPika]

Thank you @Mugen87