Add a new regexp to also match uri in the form /proxy/{{port}}

[micedre]

closes #14595

Description

This PR add a pattern to match, used with the preview subcommand to reload the page

Checklist

I have (if applicable):

• referenced the GitHub issue this PR closes
• updated the appropriate changelog in the PR
• ensured the present test suite passes
• added new tests
• created a separate documentation PR in Quarto's website repo and linked it to this PR

[posit-snyk-bot]

✅ Snyk checks have passed. No issues have been found so far.

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