Sample Scene: Add PrimaryPointerExample to MRTK3

[AMollis]

This issue has been migrated a new MRTK repository, and the status of this issue will now be tracked at the following location:

• https://github.com/MixedRealityToolkit/MixedRealityToolkit-Unity/issues/137

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MRTK2 Scene Name

PrimaryPointerExample

Overview

This example shows how to keep track of the primary pointer using primary pointer changed events. The PrimaryPointerHandlerExample script uses those events to apply a highlight to the cursor of the current primary pointer.

Additioanl Context

• MRTK2 sample uses CoreServices.InputSystem?.FocusProvider?.SubscribeToPrimaryPointerChanged
• If possible, MRK3 sample should demonstrate similar behavior using XRI

[AMollis]

Cutting this sample.