Fix/101: Type 'GLTFActions' constraint to 'AnimationClip'

[rafelis1997]

What kind of problem this solves

• - Bug Fixes
• - New Feature
• - Breaking Change
• - Documentation Updates

Context

This PR look to solve the problem addressed on the Issue 101:
issue-101

The solution proposed by @Glavin001 seams to be great and solve the issue with good clean types reducing complexity on useAnimation hook.

How to test

• Run the the gltfjsx.js file
• Import .glb | .gltf file
• Look for a typed JSX the follows this standard:

 // ...
 interface GLTFAction extends THREE.AnimationClip {
   name: ActionName;
}
// ...
type GLTFResult = GLTF & {
  nodes: {
// ...
  }
  materials: {
// ...
  }
  animations: GLTFAction[];
}
// ...
const { actions } = useAnimations(animations, group);

Issue

issue-101