docs: Use Markdown Video tag instead of iframe

[morning4coffe-dev]

GitHub Issue (If applicable): part of https://github.com/unoplatform/uno-private/issues/453

PR Type

What kind of change does this PR introduce?

• Refactoring (no functional changes, no api changes)
• Documentation content changes

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• Docs have been added/updated which fit documentation template (for bug fixes / features)
• Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Validated PR Screenshots Compare Test Run results.
• Contains NO breaking changes
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[agneszitte]

@morning4coffe-dev Also be careful here when using closes here as it will automatically close the related issue when this PR is merged.

If it is working, we will need to update more than the Uno repo here, so multiple PRs will be needed for https://github.com/unoplatform/uno-private/issues/453.

cf. https://github.com/search?q=org%3Aunoplatform+src%3D%22https%3A%2F%2Fwww.youtube-nocookie.com%2Fembed%2F&type=code with all the repos where we are using <iframe /> at the moment

[morning4coffe-dev]

Thank you @agneszitte, I updated the PR to be a part of. I didn't realize that otherones couln't be part of this PR.

[unodevops]

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-16305/index.html

[morning4coffe-dev]

Hmm, this is the resultof the Markdown Video tag:

[MartinZikmund]

Is it possible that this would work without the > at the beginning?