Monthly scheduling

[caalberts]

Similar to #56, I'm in a situation where I need to perform a job at a monthly interval. For example, every first of the month.

@plashchynski , if you're okay, I'm keen to work on this feature.

To get some context, I'd like to know if you have had initial thought around this feature. Were there specific reasons why monthly interval is not supported?

If this is a good feature to add, what kind of DSLs should be supported? Some ideas I have:

Crono.perform(Job).every 1.month, on: 1, at: {hour: 12, min: 30} # specify date and time
Crono.perform(Job).every 1.month, on: 2 # specify date only with default time

[cseelus]

@caalberts Do you know if this is supported by now?