Add OnShownDateChangedCommand so we can take action when date is changed

[Jon2G]

Changes:

• Add OnShownDateChangedCommand so we can take action when date is changed
• Update Maui packages
• Move MultiSelectionEngine to SelectionEnginesFolder
• RangeSelection not considering disabled dates
• Allow to programmatically clear selected day(s)

[yurkinh]

Hi @Jon2G Thanks for this great PR. I will check and test it locally and then will submit new version with nuget