GLTFLoader: Add loadNode hook (#25077)

examples/jsm/loaders/GLTFLoader.js

@@ -2540,7 +2540,11 @@ class GLTFParser {
 					break;
 
 				case 'node':
-					dependency = this.loadNode( index );
+					dependency = this._invokeOne( function ( ext ) {
+
+						return ext.loadNode && ext.loadNode( index );
+
+					} );
 					break;
 
 				case 'mesh':