Don't let the background worker jelly too many messages into the queue if the...

Don't let the background worker jelly too many messages into the queue if the user is off doing something else.

src/background.ts

@@ -63,11 +63,13 @@ js.time_limit = 0;
 let now = time();
 let sscan = now - 30;
 while (!js.terminated && !queue.orphan) {
+	if (queue.write_level < 10) { // Command shell isn't reading from queue right now, so don't keep filling it
 		now = time();
 		if (now - sscan >= 30) {
 			sscan = now;
 			scanSubs();
 		}
 		scanInstantMessages();
+	}
 	mswait(1000);
 }