Okay, let's do it sentence by sentence.

    [Doctests][1] are executable usage examples sometimes found in "docstrings".

It sounds like these examples are written in a specific way to be tests (of your code). But doctest is making your usage examples executable. Previously they have been just documentation.

    JavaScript doesn't have docstrings, but inline documentation can be included
in code comments.

An unaware person reading this could think: "I have no idea what docstrings are but seems like I don't have to know. Why are they telling me? What do they mean with inline documentation? It is somehow connected to docstrings but without knowing about them I don't know what they mean."

That is all I tried to address with my changes but I am totally fine with your version. We come to a detail level which is not productive with two people. To improve this text further you would have to give different versions of the text to a lot of people and ask them to rate them. I guess, most people interested in this project understand all our versions.