feat request: Add practice questions also

[staru09]

First of all thanks for creating hello-algo, it really an amazing project. Theory, examples, illustrations everything is great. I just wanted to ask if some practice questions can be added (codeforces, leetcode etc.) after every chapter just to review whatever one has learnt.
Instead of adding questions, the links can also be added via a qr code maybe.

[krahets]

I had considered this before. Adding practice questions could help readers review what they’ve learned, but it would also increase the overall learning time, which runs counter to the goal of the book.

Overall, I recommend practicing LeetCode problems after completing the entire book, rather than after each chapter. This is an interesting open question, so let’s keep this issue open for further discussion.

[staru09]

Cool, maybe we can add links to specific questions that one should practice after completing this book. It'll be helpful so one doesn't have to go through many questions and can practice in a much shorter time.