Update SMIME instructions for Linux/WSL2

[N6UDP]

Why:

Closes: https://github.com/github/smimesign/issues/30 https://github.com/github/smimesign/issues/45

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

Adding information for GPGSM on Linux and a note for both Windows and Linux about how to configure it on WSL2.

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• [ ] I have reviewed my changes in staging, available via the View deployment link in this PR's timeline (this link will be available after opening the PR).
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• [ ] For content changes, I have completed the self-review checklist.

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Source	Preview	Production	What Changed
authentication/managing-commit-signature-verification/telling-git-about-your-signing-key.md	fpt ghec ghes@ 3.11 3.10 3.9 3.8	fpt ghec ghes@ 3.11 3.10 3.9 3.8

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

[nguyenalex836]

@N6UDP Thanks for opening a PR! ✨

It looks like this is still a draft. Could you ping me when this is ready? Then, I'll get it up for review ⚡

[N6UDP]

@nguyenalex836 this should be good to go now.

[nguyenalex836]

@N6UDP Awesome, thanks for letting me know! This has been triaged for review ✨

[jc-clark]

Hey @N6UDP thank you for the contribution. We checked in with our engineering team on this and GitHub doesn't officially support gpgsm. As such, we won't add documentation to our public docs for this use case. I'll go ahead and close this PR.

[N6UDP]

@jc-clark even we don't want to add docs related to gpgsm you all should clarify the existing docs as they currently imply that smimesign is supported on linux which it is not.

[jc-clark]

I see what you're saying here, @N6UDP thank you for the feedback. I can work with our team on the best follow up for that.

[jc-clark]

@N6UDP We had a chance to chat about this and you're right that the docs currently imply that smimesign is supported on linux.

So we should fix that.

For this, we should make sure the x.509 information only shows up for the Mac and Windows versions of this doc and doesn't show up for Linux.

We can do that by replacing line 123 with the following:

{% windows %}

{% data reusables.gpg.x-509-key %}

{% endwindows %}

{% mac %}

{% data reusables.gpg.x-509-key %}

{% endmac %}

You or anyone else is welcome to open a new PR suggesting these changes.