Refactor demos and add known deployments

[timcappalli]

• Splits out demos from tools and libraries into their own section
• Adds Demos & Examples section
• Adds a list of known active deployments to help developers experience real world examples (not intended as a consumer facing list)

[cloudflare-workers-and-pages[bot]]

Deploying with    Cloudflare Pages

Latest commit:	a922712
Status:	✅  Deploy successful!
Preview URL:	https://e51cfb68.passkeys-dev.pages.dev
Branch Preview URL:	https://tc-knowndeployments.passkeys-dev.pages.dev

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[nicksteele]

I'm unable to officially review this for deploy purposes