Add a surplus workers button

It would be very nice if we could set some buildings to only take surplus workers, given that employment is rather woobly and I would like to put my spare workers on low priority things like rotary kilns or the waste sorting plant WITHOUT it giving me an annoying "not enough workers" notification. Plus it would take workers only if there's nothing else to do, just like with power, which could be pretty convenient! Also given how useless the quarantine edict is, if it was buffed a bit it would be at least a consideration combined with the ability to conveniently handle sudden changes in worker amounts.