Sorry I'm late to respond!
I would recommend using the Spine Web Player to do this. We've been improving it a lot lately, so you'll want to use version 4.0. The player handles loading and rendering the skeleton, so it's a lot less code.
We use the player like you want on our 404 error page:
You can see the code for how it's done here:
This uses data URIs to embed the skeleton JSON, atlas file, and atlas PNG but you could use regular URLs. The
a variable to adjust the mouse position in a circle, to make it so the vortex is always moving. You can remove this if you want it to look at the mouse like the owl.
If you made a tool, it would be interesting to know how it works. Did you use a game toolkit?