Bookmarking useful pages

Hello!

Before I say anything, I'd like to commend all of you on the KA team for creating such an amazing platform for learning. This website outshines all others in education.

However, there is one thing that I believe should be added. This thing is a bookmarking feature. If I could improve Khan Academy in one way, I would create a feature that allows users to save specific articles, documentation, or videos, so that they can come back to them later. This would be especially helpful for those who are having trouble grasping a concept, or, in my case, trying to compose a lesson to teach to my classmates as my final project in my math class.

Thank you guys, and keep up the amazing work!