feat: parameter to add a space under the calendar

[FDuhen]

Currently, if you use the markerMargin parameter in order to add some top margin, the rendering of the Marker can be cropped at the bottom of the Calendar.

The proposed solution would be to increase the rowHeight parameter in order to correctly handle the display of the markers. Sadly, this solution won't fit every needs.
I ended up with the solution of adding a new parameter that I called bottomSpace (could have been bottomMargin, but I thought that this name was misleading) which job is to add some more space in the AnimatedContainer rendering the Calendar, and thus allowing to correctly draw the Markers.

There might be a sexier solution to this issue, but it'd ask a lot more work and brain juice, alongside with a lot more of refactoring. With this update, it won't break anything to the current users

[FDuhen]

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