fix: wait __NEXT_DATA__ script tag evaluatable when initialize

[akagire]

Related issues

• For large page props random JSON parse error on client side #41299
• experimental: { optimizeCss: true } doesn't work with getServerSideProps after build (reading textContent) #47377
• TypeError: Cannot read properties of null (reading 'textContent') nibtime/next-safe-middleware#83

Why

When Next.js is initializing in client side, Next.js don't wait for dom loaded. Thus, some use case could not load __NEXT_DATA__ textContent. Please check related issues.

Notice that these issues may not be fully reproduced because of a specific browser, browser memory usage, caching, using an extension or something else.

Although, It can prevent by check document.readyState is not loading.

I was afraid this approach has the possibility of degrading first loaded rendering performance, so I checked Lighthouse and it didn't in create-next-app default page.

If I have forget some consideration, please tell and comment this PR.