perf(dev-cache): improve localhost markdown page navigation performance (when having 2,000+ pages)

[coffeephile]

🔗 Linked issue

#2674

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Resolves #2674

Navigating between markdown pages on localhost (dev server) is very slow when dealing with 2,000+ markdown pages.
(Please refer to linked issue for demo and reproduction)

By using cachedContents on localhost as well (not only during build time) this issue can be resolved.
In order to keep hot reload working, the cache gets flushed when a file change is detected.

I confirmed my fix to be working for my use case, however I'm not sure if I am breaking anything else in the process, so any advice or help is welcome.
This PR should be considered a first draft, rather than a perfect solution. 🙇‍♂️

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[farnabaz]

By removing the prerendering check, we are changing the behavior of the production environment too.
We should add back prerendering check and add logic to handle dev mode

[coffeephile]

@farnabaz Many thanks for your swift review, much appreciated! 🙏

I've implemented the changes you suggested, please check again 🙇‍♂️

[farnabaz]

LGTM 👍
Thanks

[coffeephile]

Thank you! 🙏😊