Add docs for saturating integer arithmetic.

[jbcrail]

This was added for #23241.

[rust-highfive]

r? @huonw

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[steveklabnik]

These should be 'examples'

[steveklabnik]

r=me with two nits, thanks!

[jbcrail]

Thanks for the comments. I've updated the branch.

On a related note, I noticed other examples have the same issues that you mentioned. Would it be too pedantic if I corrected those in another pull request?

[steveklabnik]

I've been trying to play 'boy scout rule' with them, but if you'd like to clean them up, I'd love that.

[steveklabnik]

oh, and would you mind squashing these please? thanks

[jbcrail]

I squashed the commits. I also sent a pull request to remove the Rust syntax highlighting from the example docs.

[jbcrail]

Is anything else needed to close this pull request? Thanks.

[steveklabnik]

@bors: r+

[bors]

📌 Commit 62be565 has been approved by steveklabnik

[steveklabnik]

Whoops, sorry about that! Sometimes these things slip. Thank you!

[bors]

⌛ Testing commit 62be565 with merge e98e391...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-x-android-t, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-win-32-nopt-t, auto-win-32-opt, auto-win-64-nopt-t, auto-win-64-opt