[FEATURE REQUEST] Add lock timeout

[TinF0ilHat1]

I understand large stacks must be protected with an airgapped o multi-sig solution, however sometimes an user might need to keep a fair amount on Hot wallet.
Would be very helpfull to have lock timeout after .. 1 - 5 - 10 minutes of inactivity [especially if the laptop doesn't already lock itself with a timer, see with the caffeine's usage for example]

The password is still mandatory to sign, so from a security standpoint it is ok. However if it's not an heavy work for you i would like to have this option.