Don't allow inklecate to get stuck in an infinite loop

This is primarily for Inky, not sure play mode is actually used by anyone in inklecate!

When you enter some ink that accidentally gets into an infinite loop, it hangs and makes your computer go slowly. Two things we should do:

1. Use ink's new async mode in the inklecate play mode to limit the amount of processor that it can take up, allowing the thread to sleep periodically. (e.g. allow 30ms chunks, then sleep for a bit?) This will slow down ink processing a bit for stories with complex processing though.
2. Set a time out, after which time it generates an error that can be viewed in Inky. e.g. 10 seconds?