Add 8.1.1 release notes (#8237)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Justin Anderson <[email protected]>

Author: github-actions[bot]

documentation/releaseNotes/releaseNotes.v8.1.1.md

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+Today we are releasing the 8.1.1 build of the `dotnet monitor` tool. This release includes:
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+- Updated dependencies
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+If you would like to provide additional feedback to the team [please fill out this survey](https://aka.ms/dotnet-monitor-survey?src=rn).