Add link to context availability for workflow .if key syntax

[MarkIannucci]

Why:

Closes #22436

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

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• I have reviewed my changes in staging.
• For content changes, I have completed the self-review checklist.

[welcome]

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[cmwilson21]

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

I'll get this triaged for review! ⚡

[github-actions]

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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
actions/using-workflows/workflow-syntax-for-github-actions.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

[lucascosti]

Thanks for this PR, @MarkIannucci! I've pushed up a change that adds a link to the context availability article for all the mention of .if keys.

Almost all keys are somewhat restricted in their use of certain contexts, but it is more obvious when using them for conditions in the .if keys, so I think a regular sentence will suffice here.

Thanks for the contribution, I'll get this merged.

[github-actions]

Thanks very much for contributing! Your pull request has been merged 🎉 You should see your changes appear on the site in approximately 24 hours. If you're looking for your next contribution, check out our help wanted issues ⚡

[MarkIannucci]

I like how you toned down my frustration. I also saw some nice practices in the way the docs team is using actions to deliver the docs site. I definitely feel that I learned more than I gave with this PR. Thank you :)