Support block height for reminders #1668
Description
Describe the problem you're trying to solve
Not sure there's a problem that this would solve but ...
Describe the solution you'd like
... at least two stackers think it would be cool if our @remindme bot could support relative or absolute block height.
For example: @remindme in 3 blocks or @remindme at block 888888
Describe alternatives you've considered
n/a