Add short delay to avoid blocking

[kasnder]

Usually, the script works very well for me. However, it blocks the main thread for me, and delays the start of the app. It also crashes for some apps.

The proposed change does two things:

1. It does the class dumping asynchronously, so app loading isn't delayed anymore (I think).
2. For a small number of very large apps (size more than 1GB, less than 1% of all apps), it prevents crashes, and failure of class dumping by delaying the class dumping operation.

[kasnder]

I've only tested this using frida -U -f package -l script.js so far.

Update: Seems to work with the latest ./ioshook as well.

[noobpk]

Thank you very much for your contribution.
Sometimes scripts run too fast leading to app crashes. ^^!!