[FEATURE] - Support running a job on multiple days of a month

[JohnRoesler]

Is your feature request related to a problem? Please describe

This would be nice to allow a job to run multiple days in a month vs. a single day

Describe the solution you'd like

s.Every(1).Month(15).Month(17).At("02:00").Do(func() {})

Describe alternatives you've considered

s.Every(1).Month(15).At("02:00").Do(func() {})
s.Every(1).Month(15).At("02:00").Do(func() {})

Additional context

could be done by adding a func On(day int)

s.Every(1).Month().On(15).On(17).At("02:00").Do(func() {})

[denizzengin]

Hi, i would like undertake it if it is active at present

[JohnRoesler]

Yes please go ahead! @denizzengin