feat(content-blog): support json feed

[notzheng]

Motivation

Support to generate json feed of blog posts.

Have you read the Contributing Guidelines on pull requests?

yes

Test Plan

Add test case for generating json feed.

Related PRs

None

[netlify]

✔️ [V2]
Built without sensitive environment variables

🔨 Explore the source changes: db0272d

🔍 Inspect the deploy log: https://app.netlify.com/sites/docusaurus-2/deploys/61bdefbbb83d480009b200a8

😎 Browse the preview: https://deploy-preview-6126--docusaurus-2.netlify.app

[github-actions]

⚡️ Lighthouse report for the changes in this PR:

Category	Score
🟠 Performance	81
🟢 Accessibility	98
🟢 Best practices	100
🟢 SEO	100
🟢 PWA	95

Lighthouse ran on https://deploy-preview-6126--docusaurus-2.netlify.app/

[Josh-Cena]

Thanks. I'd rather make it opt-in as we have stated in our docs that RSS & Atom are generated by default (which IMO is already a little too much—I'd rather only generate RSS unless otherwise stated). Apart from that, LGTM👍

Made some refactors. If you don't have anything further to add, we can merge this

[notzheng]

Thanks. I'd rather make it opt-in as we have stated in our docs that RSS & Atom are generated by default (which IMO is already a little too much—I'd rather only generate RSS unless otherwise stated). Apart from that, LGTM👍

Made some refactors. If you don't have anything further to add, we can merge this

Thanks for your advice and refactors.