It looks like the spine-webgl runtime is missing the outline option.
Is there any plan to support it or is there some way to have it or resources/pointer to get it working there ?
We don't plan on adding it, as there's no genreralized way to do it that works in all situations with WebGL. It depends on what states you set up for your app, what rendering buffers you're using (stencil? depth?), and so on.
You can try to find resources on simple outline shaders on the web, then use the Shader class of spine-ts WebGL:
If you're using SceneRenderer to draw your scene, you can set the shader it uses to draw skeletons via this field: