[Feature] Make day selection optional

[Psycoguana]

Hello! First of all, amazing library, thanks a lot for supporting it. It has a bunch of great features.

Is your feature request related to a problem? Please describe.
I need to have a calendar which allows to select year and month. The date is not necessary, but currently (as far as I know) there is no way to make the day selection optional.

Describe the feature you'd like
It'd be great to pass a bool like disableDaySelection, the day could be some default like 01.
Then when using showCalendarDatePicker2Dialog it would display the month selection, when selecting a month and clicking the ok button, it would close the dialog.

Use cases
This would be useful to select the data that must be shown for a particular month. Since it's for the whole month, there is no need to select a day.