[gltf-part] does not respect draco compression settings in scene

[kfarr]

Issue:
If the scene entity has a draco decoder defined in gltf-model attribute such as "dracoDecoderPath: src/lib/;" it is not utilized in the gltf-part component and thus the part will not be loaded and the following error is displayed in the console:
Error: THREE.GLTFLoader: No DRACOLoader instance provided.

Expected behavior:
If gltf-model attribute is defined in scene entity and gltf-part is used to load a draco encoded gltf / glb file then the file should decode and display as expected

[kfarr]

I was able to get this working:
https://github.com/kfarr/streetmix3d/blob/master/src/components/gltf-part-draco.js

Not sure if useful to submit pull request as I think my method is a bit hacky to get the draco loader in the init function of the gltf-part component:
this.dracoLoader = document.querySelector('a-scene').systems['gltf-model'].getDRACOLoader();

[kfarr]

I solved this issue by forking the repo and making gltf-part-plus component which supports draco decompression:
https://github.com/kfarr/aframe-gltf-helpers#gltf-part-plus