CC-7056: add containers registries credentials command reference

[martinezjandrew]

Summary

Add command reference for wrangler containers registries credentials - a command to generate temporary push/pull credentials for the Cloudflare managed registry.

Documentation checklist

• Is there a changelog entry (guidelines)? If you don't add one for something awesome and new (however small) — how will our customers find out? Changelogs are automatically posted to RSS feeds, the Discord, and X.
• The change adheres to the documentation style guide.
• If a larger change - such as adding a new page- an issue has been opened in relation to any incorrect or out of date information that this PR fixes.
• Files which have changed name or location have been allocated redirects.

[elithrar]

/bonk review this and suggest changes

[ask-bonk]

No issues that would block merge. One minor consistency note posted inline.

[ask-bonk]

Review posted. No issues that would block merge — the content is correct, follows the established pattern for command reference entries, and the MDX is valid. Posted one inline suggestion about aligning the <DOMAIN> vs [DOMAIN] bracket convention with the sibling registries commands.

github run