meta: Add CODEOWNERS (for replay only)

[billyvg]

This was previously removed, but we are re-adding for just Replay related items.

Closes #6477

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	20.61 KB (0%)
@sentry/browser - ES5 CDN Bundle (minified)	64.39 KB (0%)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	19.16 KB (-0.01% 🔽)
@sentry/browser - ES6 CDN Bundle (minified)	56.77 KB (0%)
@sentry/browser - Webpack (gzipped + minified)	21.62 KB (0%)
@sentry/browser - Webpack (minified)	72.03 KB (0%)
@sentry/react - Webpack (gzipped + minified)	21.64 KB (0%)
@sentry/nextjs Client - Webpack (gzipped + minified)	51.99 KB (+0.02% 🔺)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	28.15 KB (+0.03% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	26.36 KB (+0.04% 🔺)
@sentry/replay ES6 CDN Bundle (gzipped + minified)	44.47 KB (+0.01% 🔺)
@sentry/replay - Webpack (gzipped + minified)	38.54 KB (0%)
@sentry/browser + @sentry/tracing + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	63.13 KB (+0.02% 🔺)
@sentry/browser + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	56.22 KB (0%)