Static Site Generation with dynamic route fallback

Test 1:This timestamp 👉 should be when the `npx open-next build` was run, not when the page is refreshed. Hence, this time should not change on refresh.js

Test 2:This string 👉 "" should be "First post"

Test 3:Check your browser's developer console. First request might show cache MISS on first load. Subsequent refreshes should shows cache HIT.