Subscription Support

**Is your feature request related to a problem? Please describe.**

I have a requirement for a stitching library that also supports subscriptions.

**Describe the solution you'd like**

I would like to see this library updated to support subscriptions.

**Describe alternatives you've considered**

Braid and Lilo do not support subscriptions. I have started reviewing the code base to try and understand how to effectively implement the subscriptions, though, it looks like it may take considerable work to my untrained eye.