Typo s/imposible/impossible (#802)

Noticed a small typo.

README.md

@@ -420,7 +420,7 @@ const scheduler = new NodeResque.Scheduler({
 
 Sometimes a worker crashes is a _severe_ way, and it doesn't get the time/chance to notify redis that it is leaving the pool (this happens all the time on PAAS providers like Heroku). When this happens, you will not only need to extract the job from the now-zombie worker's "working on" status, but also remove the stuck worker. To aid you in these edge cases, `await queue.cleanOldWorkers(age)` is available.
 
-Because there are no 'heartbeats' in resque, it is imposable for the application to know if a worker has been working on a long job or it is dead. You are required to provide an "age" for how long a worker has been "working", and all those older than that age will be removed, and the job they are working on moved to the error queue (where you can then use `queue.retryAndRemoveFailed`) to re-enqueue the job.
+Because there are no 'heartbeats' in resque, it is impossible for the application to know if a worker has been working on a long job or it is dead. You are required to provide an "age" for how long a worker has been "working", and all those older than that age will be removed, and the job they are working on moved to the error queue (where you can then use `queue.retryAndRemoveFailed`) to re-enqueue the job.
 
 If you know the name of a worker that should be removed, you can also call `await queue.forceCleanWorker(workerName)` directly, and that will also remove the worker and move any job it was working on into the error queue. This method will still proceed for workers which are only partially in redis, indicting a previous connection failure. In this case, the job which the worker was working on is irrecoverably lost.