Add drawing started, cancelled, and on-drawing commands

[VladislavAntonyuk]

This commit adds the following changes:

• Added DrawingStartedCommand to handle the event when drawing starts.
• Added DrawingCancelledCommand to handle the event when drawing is cancelled.
• Added OnDrawingCommand to handle the event while drawing.

These changes allow for better control and handling of the drawing events in the DrawingViewPage.xaml and DrawingViewViewModel.cs.

Description of Change

Linked Issues

• Fixes Why does DrawingView doesn't have DrawingLineStarted event or DrawingLineMoved event? #1419

PR Checklist

• Has a linked Issue, and the Issue has been approved(bug) or Championed (feature/proposal)
• Has tests (if omitted, state reason in description)
• Has samples (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Changes adhere to coding standard
• Documentation created or updated: https://github.com/MicrosoftDocs/CommunityToolkit/pull/329/files

Additional information

[brminnick]

Thanks Vlad!!

Could you add the docs for the new APIs? I went ahead and added the approved This Proposal has been approved and is ready to be added to the Toolkit , do not merge Do not merge this PR , and pending documentation This feature requires documentation labels here so that we don't forget.

I'd love for us to publish v6.1.0 this week before our standup! So if you're able to submit a Docs PR either tomorrow or Wednesday, we can merge this in for v6.1.0 which'll be our final release before .NET 8!!

I went ahead and implemented the new IDrawingView.OnDrawingLineCompleted(IDrawingLine) API implementing it as a Default Interface Implementation. This avoids breaking changes to our users while still allowing us to implement the new API under the hood. This'll make our lives easier when we remove the Obsolete API in a future PR.

/// <summary>
/// Event occurred when drawing line completed
/// </summary>
/// <param name="lastDrawingLine">Last drawing line</param>
void OnDrawingLineCompleted(IDrawingLine lastDrawingLine) => OnDrawingLineCompleted(lastDrawingLine);

/// <summary>
/// Event occurred when drawing line completed
/// </summary>
/// <param name="lastDrawingLine">Last drawing line</param>
[Obsolete($"Use {nameof(OnDrawingLineCompleted)} instead.")]
void DrawingLineCompleted(IDrawingLine lastDrawingLine);

[VladislavAntonyuk]

@brminnick documentation PR is ready