add example to search by not author

[aczechowski]

Why:

Closes https://github.com/github/docs/issues/22902

What's being changed (if available, include any code snippets, screenshots, or gifs):

Added an example showing how to search by -author with a brief explanation

Check off the following:

• [x] I have reviewed my changes in staging (look for the "Automatically generated comment" and click the links in the "Preview" column to view your latest changes).
• [x] For content changes, I have completed the self-review checklist.

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Automatically generated comment ℹ️

This comment is automatically generated and will be overwritten every time changes are committed to this branch.

The table contains an overview of files in the content directory that have been changed in this pull request. It's provided to make it easy to review your changes on the staging site. Please note that changes to the data directory will not show up in this table.

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Content directory changes

You may find it useful to copy this table into the pull request summary. There you can edit it to share links to important articles or changes and to give a high-level overview of how the changes in your pull request support the overall goals of the pull request.

Source	Preview	Production	What Changed
search-github/searching-on-github/searching-issues-and-pull-requests.md	fpt ghec ghes@ 3.7 3.6 3.5 3.4 3.3 ghae	fpt ghec ghes@ 3.7 3.6 3.5 3.4 3.3 ghae

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fpt: Free, Pro, Team ghec: GitHub Enterprise Cloud ghes: GitHub Enterprise Server ghae: GitHub AE

[cmwilson21]

@aczechowski Thank you for opening a PR and linking it to your issue! ✨

I noticed this was still a draft PR. Is it ready for review? If so, let me know and I'll go ahead and triage it for review! 💖

[aczechowski]

Thanks @cmwilson21 - I just hadn't yet looked at the preview yet. I was waiting for the build but then signed off for the day before it finished. 😄 Looks good to me, but let me know if there are any needed or suggested changes.

[cmwilson21]

@aczechowski No prob, thanks for letting me know! I'll get this triaged for review!

Just a heads up, we are a bit a slow right now as many of our team members have taken time off for the holidays. Someone will have eyes on this soon 👍

[felicitymay]

https://github.com/github/docs/issues/23461 raised

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