Add the ability to change the unit of time and/or do simple math in the time field when disabling

[christasich]

Is your feature request related to a problem? Please describe.
No. This is not related to a problem. Fairly often I disable my pi-hole for various reasons and different lengths of time. The length of time depends on the task. I keep my default set to 300 s (5 min), but very often I find myself doing the math to disable it for 30 min or an hour.

Describe the solution you'd like
Ability to change the unit of time to minutes or hours. It would also be great if the field could do simple math (e.g. entering "100*3" converts to "300").

Describe alternatives you've considered
Trying to do math in my head but inevitably using a calculator. :)