suggestion: add a property to recognize whether the graph instance is interrupted

[vianvio]

Thanks for the great update of implementing intrerrupt and Command resume, I have integrated these features in my app, but found it unclear to figure out whether the instance is interrupted.

currently I'm using next node for check

const nextNode = (await flowInstance.getState(config)).next;
if (Array.isArray(nextNode) && nextNode.length > 0) {
  // do something
}

and I find the test case is using number of tasks on state for check

const currTasks = (await graph.getState(config)).tasks;
expect(currTasks[0].interrupts).toHaveLength(1);

Both should work but not good I think, can we have a property like isInterrupted or interruption: true, that would be more friendly to use