calculated shift for astro triggers

[fonebone42]

Is your feature request related to a problem? Please describe.
I'd like to see support for Astro triggers in Blocky that allow for a calculated shift rather than just a fixed value one. For example I'd like to use a random value to say "trigger randomly between 5 and 15min after subset"

Describe the solution you'd like
allow using an expression instead of only a constant for the time shift. The value should be recalculated for each trigger event.

Describe alternatives you've considered
without one needs to have a sunset trigger followed by a delayed execution which allows for calculated delays ... the requested option would be a lost simpler and much more readable

Additional context
the first block is what you need to do today, the second constructed one is what I'd like to become able to do