Added OutlinedButton code sample

[Abhishek01039]

related to #75642

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• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
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• I listed at least one issue that this PR fixes in the description above.
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[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie on the #hackers channel in Chat.

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[Abhishek01039]

Hello @HansMuller
can you please review this PR?
Thanks

[HansMuller]

LGTM