Update actions expression documentation for ternary like behaviour

[Megagyger]

Why:

Closes #24355

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

Added documentation and an example of how you can achieve ternary operator behaviour using GitHub Actions expressions.

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[github-actions]

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Source	Preview	Production	What Changed
actions/learn-github-actions/expressions.md	fpt ghec ghes@ 3.9 3.8 3.7 3.6 3.5 3.4 ghae	fpt ghec ghes@ 3.9 3.8 3.7 3.6 3.5 3.4 ghae

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

[cmwilson21]

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

I'll get this triaged for review! ⚡

[Megagyger]

HI @cmwilson21, just wondering on the status of this, is it a candidate to be reviewed and merged or should I just forget about it.

[cmwilson21]

Hi @Megagyger - Thanks for checking in! This PR is on the board waiting for review. We are currently working through our backlog and we appreciate your patience.

Someone will review it soon 💖

[SiaraMist]

Hey @Megagyger, thank you so much for adding this example to the docs! And for your patience as we work through our backlog. 💛

This is a really helpful example of behavior I'm sure people will find useful. I'm going to make one small formatting edit, and then 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 ⚡

[piotrekkr]

@Megagyger Thank you so much for this example. Before this I was not aware it was even possible to have ternary operator in expressions. I mostly used bash conditions to achieve same effect but now I don't have to 👍

PS I wonder how long was it possible but undocumented. Do you know this?

[rdhar]

I don't know how long it's been around for either, but I really appreciate having basic if/else or ternary operators.

It's particularly helpful in reusable workflows like this where many inputs may or may not exist, and we have to supply default/fallback values accordingly, while still formatting or manipulating the variables on-the-fly as well.