added coin change problem

[Devil1729]

[ ] Mark me as completed

• [x] My Pull Request adheres to the Contribution guidelines.
• [x] I have added problem.md and solution files in the appropriate folder.
• [x] In problem.md I have provided a correct link to the problem.
  (In case you are not adding a problem, you can freely mark this as complete)
• [x] The solution I have given is my own and not plagiarized in any form.
• [x] My solution passes all the testcases within the given constraints.
• [x] I have properly indented and documented my solution using comments.
• [x] I agree that all the above marked are true to the best of my knowledge and my PR can be closed if found otherwise.

All marked as completed

[boring-cyborg[bot]]

Hi there :wave: Congratulations on sending your first PR here :sparkles: Your PR will be reviewed soon, in the meantime it would be great if you could star :star: this repo :smiley:

[stale[bot]]

This Pull Request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale[bot]]

Closing due to lack of response.