Proposal - Randomized delay

[Kein]

Follow up to #149

There is already a way to define custom delay and push it further if API responds negatively. What would be also nice to have a randomized delay between minX and maxY that will serve some kind of imitation of a period similar to when a human user has to scroll up and find new message to delete.

tl;dr avoid uniform delays between deletions, they are easily detectable.

[gohamstergo]

#342