Add Edabit as a resource for learning JavaScript

Once someone is familiar with the basic syntax and semantics of JavaScript using one or more learning resources, a basic pattern is to practice the rudiments of algorithmic problem solving with a site such as CodeWars. From a pedagogical point of view, I think that [Edabit](https://edabit.com/challenges/javascript) is far superior, primarily because associated to each problem are resources that give the information to help solve the problem. This way, a learner would be directed to systematically learn about various documentation and resources, while solving a specific problem (which is the basic pattern of self-teaching how to code). This solves the problem of giving someone starting the task of doing blind searches for information, as spoken of in the promotional video [here](https://www.youtube.com/watch?v=i9HDBXOSX-0).

More generally, I suggest more explicit advice about how to practice the materials in the READMEs.