types (GLTFLoader): add definitions about plugin system

[0b5vr]

Add type definitions about GLTFLoader plugin system which is introduced in #19144 .

Points need review

• I used a name GLTFLoaderPlugin as an interface name, which is not explicitly mentioned in anywhere yet. is the name appropriate?
• I'm not sure I should have _markDefs in this definition
• I don't have enough confidence about return type of:
  • getMaterialType, returns typeof Material | null.
  • extendMaterialParams, returns Promise<any>
  • These are working fine in my WIP project at least

[donmccurdy]

looks good, thank you!

[donmccurdy]

I'm not sure I should have _markDefs in this definition...

It might be better to hide this one.. i'd be OK with it being a public method, if someone eventually needed it, but if so it should not be prefixed with an underscore.

[takahirox]

Yes, _markDefs should be hidden (or we should remove the prefix '_').

When I implemented the lights extension with the plugin system, I couldn't avoid to extend _markDefs. But the method is for a bit too internal use. So I'd like to come up with a nicer way and somehow remove _markDefs extension at some point...

[donmccurdy]

Let's omit it from type defs for now, then. We can un-prefix it and add it later, if it turns out we can't remove it and other extensions need it.

[takahirox]

Looking good to me (other than exposing _markDefs as commented)

[mrdoob]

/ping @fms-cat

[0b5vr]

thanks for the ping!

gonna delete the definition of _markDefs.

[0b5vr]

@mrdoob ready!

[mrdoob]

Thanks!