(#3108) Add PR example

[pauby]

Description Of Changes

Added a great PR example to the CONTRIBUTING.md file.

Motivation and Context

We need a good example to help people when contributing.

Testing

This is just a change to a markdown document.

Operating Systems Testing

N/A

Change Types Made

• Bug fix (non-breaking change).
• Feature / Enhancement (non-breaking change).
• Breaking change (fix or feature that could cause existing functionality to change).
• Documentation changes.
• PowerShell code changes.

Change Checklist

• Requires a change to the documentation.
• Documentation has been updated.
• Tests to cover my changes, have been added.
• All new and existing tests passed?
• PowerShell code changes: PowerShell v2 compatibility checked?

Related Issue

#3108

[gep13]

LGTM!

[gep13]

This is simply a change to the contributing document, so we don't need to wait for the CI builds to finish. Going to move forward with merging this.

[gep13]

@pauby thanks for getting this updated!