Add option to add time offset when using automatic mode

[mmacura311]

Is your feature request related to a problem? Please describe.
I am using the extension in automatic mode to adopt to sunrise and sunset. It would be great if I could specify a time offset/delay when the theme is changed, so do not change immediately when there is sunset time, but after specified delay

Describe the solution you'd like
When selecting the radio button for "Automatically set sunrise/sunset times (requires location)" the addon could have a setting option to enter delay in minutes, so user can set switch to dark mode later, eg +60 minutes
few options come to mind:
a) have only one input box where user can enter integer. The time delay would happen positvely for sunrise and negatively for sunset (so if user enters 30 the dark mode switch would be 30 minutes after sunset and 30 minutes before sunrise)
b) have 2 boxes to specify offset both for sunrise and sunrise. Positive integer would delay the action and negative integer would make it happen earlier.

Additional context
Using manual mode is not sufficient as during spring and autumn the sunset and sunrise time change a lot.
Also some timezones are very big so the local time may not actually represent sunrise and sunset times, so the user could use this option to adjust.