Return something for React effect cleanup for autofill?

[Firehed]

I'm not sure if this is possible/easy, but in order to nicely clean up React effects (when the SDK is used in a React context), it would be beneficial to expose something that allows for cleanup. This could be a premade function, the abort controller, or something else.

The SDK does most of the important cleanup so this isn't a huge issue, but it would help keep consuming codebases tidier and less full of surprises.

[Firehed]

Now that signal handling has improved a lot, I think the way to go here (if it's needed at all) would be something to the effect of () => signal.abort('Manually canceled')

[Firehed]

Based on some local experimentation, I think al that needs to happen here is a) change cancelPendingRequests() from private to public, and b) adjust the message sent to the abort controller, for clarity.