Step 1: Take note of all the keyframe times in your animation.

Step 2: Use the game exporter to export your animations of those keyframes. Make sure the first animation is the 'idle' animation, as this will be returned to when any other animation is stopped.

Step 3: Follow the following guide to convert the animation using the command line tool converter:
​http://help.plattar.com/assets-and-content/advanced-topics/converting-fbx-to-gltf-using-fbx2gltf

Step 5: Zip up the result and upload to Plattar
Step 6: Create your annotations and select which animation you want them to play.