feat: add skeleton animation & vertex aimation

[JiepengTan]

project file 06-Skeleton.zip

config file : "assets/sprites/Tom/index.json" skeleton animation

{

   ... // other fields
  "animator": "skeleton.animator",
  "avatar": "skeleton.avatar",
   ... // other fields
}

vertex animation

{
   ... // other fields
  "animator": "vertex.animator",
  "avatar": "vertex.avatar",
   ... // other fields
}