Add test for append animation and detach animation methods#5103

diegoteran merged 3 commits intogoogle:mastergoogle/model-viewer:masterfrom

mohammadbaghaei:add-test-for-appendAnimation-and-detachAnimation-methodsmohammadbaghaei/model-viewer:add-test-for-appendAnimation-and-detachAnimation-methodsCopy head branch name to clipboard