List all text runs

[tobiasandersen]

We're building a UI for interacting with Rive graphics (that aren't built by us), and we want to automatically expose all inputs and text runs to the user. Currently we can easily detect which inputs are available with the stateMachineInputs() method — but I don't think it's possible to do for text runs?

It would be fantastic to have a similar method for retrieving text runs, e.g. textRuns(). Alternatively #359 could also work for us, but I still think this method makes sense.

[HayesGordon]

Closing this as a duplicate of #359. I'll provide more information there.