add: disconnected time tolerance

[pZacca]

I (and 325k people) use Reload extension.

The problem is: when the reload button is hit, time resets making me lose all my counted time.

My suggestion is: add a tolerance time (customizable by user) to be out of VSC without resetting time count so connection instabilities, accidental closing and reloads doesn't make you unfairly lose your counting.

Maybe add a limit to this config so mal-intended users can't pretend to be active?