[Workers] Mark Custom Branch Aliases as supported in Pages compatibility matrix

[neelakolkar-cf]

Closes #22709

Summary

Updates the "Custom Branch Aliases" row in the Pages to Workers compatibility matrix from ⏳ (coming soon) to ✅ for Workers. Adds a footnote that links to custom domain Preview URLs and explains how they differ from Pages branch aliases.

Why

Worker Previews (changelog 2026-09-22) can serve Preview URLs on a custom domain, at <preview-name>.<your-domain>. The Preview name defaults to the Git branch. This covers the use case in #22709: branch previews on your own domain, for example to share cookies with production. The matrix still listed the feature as coming soon.

It is not exactly the same as Pages, so the footnote explains the difference. Pages lets you point any hostname at a branch. Workers uses <preview-name>.<domain> with a wildcard DNS record and certificate.

Note on footnote numbering

The site's Markdown renderer (remark-gfm) numbers footnotes in the order they are referenced, not by their labels. The new reference comes before the existing [^5] and [^6], so those are renamed to [^6] and [^7]. The hardcoded "As in ⁵" in the Pages Plugins footnote is updated to ⁶ so it still points to the File-based Routing footnote. The footnote wording is unchanged. I rendered the section with remark-gfm to confirm the footnotes appear as 1–7 in order.

Documentation checklist

• Is there a changelog entry (guidelines)? Not needed. Worker Previews already has a changelog entry.
• The change adheres to the documentation style guide.

[cloudflare-docs-bot]

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