Add checkbox to easily track progress for learners

[Developer-Y]

Thanks for all the effort, I am sorry, but I prefer not to merge this PR for following reason: It will increase everyone's effort while creating the Pull requests, not adding the checkbox means the list is inconsistent. Anyone should be able to contribute, so I keep the list using most basic markdown only. I don't even know how to add checkbox or how to select them. Also, if there are 20 Algorithms courses or 30 ML courses in list, people are going to go through 1-2 courses only, rest is going to be empty.

[unobatbayar]

Thank you, that's actually true. I'll close this merge request.