Set up blog redirects

[schultek]

Setup redirects from blog.flutter.dev to flutter.dev/blog.

I verified the redirect rules locally for all posts.

Contributes to #13507

[gemini-code-assist]

Code Review

This pull request introduces a new blog_redirects site with Firebase hosting configuration, including redirect rules to https://flutter.dev/blog and a fallback HTML redirect page. Feedback points out that the firebase.json file is missing the required top-level emulators configuration block, which will cause the verify-firebase-json presubmit check to fail.

[flutter-website-bot]

Staged preview of the updated docs.flutter.dev site (updated for commit a1c395d):

https://flutter-docs-prod--docs-pr13632-blog-redirects-xeafdpd0.web.app

[flutter-website-bot]

Staged preview of the updated flutter.dev site (updated for commit a1c395d):

https://flutter-dev-230821--www-pr13632-blog-redirects-k9gd8bx5.web.app

[mit-mit]

Deployed to https://flutter-blog-redirects.web.app

[mit-mit]

Seems to work; tested with these:

• https://flutter-blog-redirects.web.app/learning-faster-with-antigravity-cd735bfe44e7
• https://flutter-blog-redirects.web.app/whats-new-in-flutter-3-35-c58ef72e3766
• https://flutter-blog-redirects.web.app/https-medium-com-flutter-io-announcing-flutters-beta-2-c85ba1557d5e

[parlough]

@schultek Thanks for this, looks good to me.

Before landing though, can you add trailing new lines to the files and add a basic README to the directory explaining what it's for?