add link to quickstart video toward top of quickstart doc

[valanm22]

Signed-off-by: Valan Baptist Mathuranayagam valanm22@gmail.com

What this PR does / why we need it: Added the YouTube link to quickstart.md

Special notes for your reviewer:

If applicable:

• [x] this PR contains documentation
• [ ] this PR contains unit tests
• [ ] this PR has been tested for backwards compatibility

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[krancour]

@valanm22 thank you so much for the contribution!