Refactor App component

[palagdan]

• [x] Bump react-router-dom to v6
• [x] Remove react-imported-component as it is no longer needed and does not impact optimization.

[palagdan]

react-imported-component behaves the same as React's lazy with Suspense; it splits components into chunks and loads them only when needed. However, I believe it's unnecessary for this application since react-imported-component is a third-party library that is not being utilized effectively, with only about 3,000 downloads per month. Therefore, I will refactor the code using react-router-dom. This will provide similar functionality while making the code simpler and more readable.