FluentCalendar, FluentDatePicker and FluentTimePicker components

[dvoituron]

FluentCalendar, FluentDatePicker and FluentTimePicker components

📖 Description

This PR adds the FuentCalendar, FluentDatePicker and FluentTimePicker components, as well as the associated unit tests.

The calendar features a Culture property to display days in the user's language. By default, the OS culture is used. It is possible to disable certain dates using the DisabledDateFunc function, which returns a boolean, depending on the date proposed. If required, the developer can fully customize the visual of a day via the DaysTemplate.

An extension method ToTimeAgo(TimeSpan delay) returns a string with one of these samples, depending of the delay: "Just now", "25 seconds ago", "14 minutes ago", ...

✅ Checklist

General

• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.

Component-specific

• I have added a new component
• I have modified an existing component

Breaking changes

Old FluentCalendar	New FluentCalendar
✅ Readonly	No change - Case updated to ReadOnly to be coherent.
✅ Locale	⚠️ Culture This property is a CultureInfo object more precise to customize rendering (including first day of week: Sunday, Monday, ...).Migration from Locale ("fr-FR") to Culture: System.Globalization.CultureInfo.GetCultureInfo("fr-FR")
✅ Month & Year	PickerMonth This new property is more Blazor/C#, because it's a DateTime object. And a two-way bindable property.
✅ DayFormat	No change
🚫 WeekdayFormat	⚠️Breaking change - No implementedUse the Abbreviated value of .NET system weekday names.
🚫 MonthFormat	⚠️Breaking change - No implementedUse the Full month name.
🚫 MinWeeks	⚠️Breaking change - No implemented
🚫 OutOfMonthSelectable	⚠️Breaking change - No implemented
✅ DisabledDates & DisabledSelectable	DisabledDateFunc This property is a function. More interesting if you have a lot of dates to deactivate. You can create a function to get these dates from a DB and not fill a large array of dates in memory.DisabledSelectable True to display the Strikethrough style. False to display the day like other, but not selectable.
⬜ SelectedDates & SelectedDatesChanged	SelectedDate & SelectedDateChangedAt this moment, only one date is selectable
✅ OnDateClicked	No change
🚫 ChildContent	⚠️Breaking change - Removed

[LuohuaRain]

I am wondering if the value of FluentDatePicker should be of the DateOnly type, and if the value of FluentTimePicker should be of the TimeOnly type?