GLTFLoader: Honor Firefox version when checking for ImageBitmap. (#23909)
GLTFLoader: Honor Firefox version when checking for ImageBitmap. (#23909)

* GLTFLoader: Honor Firefox version when checking for ImageBitmap.

* GLTFLoader: Clarify ImageBitmap check.

* GLTFLoader: Clean up.

* GLTFLoader: More clean up.
aardgoose/three.js,gero3/three.js,greggman/three.js,Liuer/three.js,mrdoob/three.js,aardgoose/three.js,makc/three.js.fork,06wj/three.js,makc/three.js.fork,gero3/three.js,WestLangley/three.js,donmccurdy/three.js,WestLangley/three.js,greggman/three.js,mrdoob/three.js,Liuer/three.js,06wj/three.js,donmccurdy/three.js