They did have something that was intended to evolve into something like that, I think, but it was half-hearted, somewhat tucked away, and never gained any real

They did have something that was intended to evolve into something like that, I think, but it was half-hearted, somewhat tucked away, and never gained any real traction: https://developer.mozilla.org/en-US/docs/Archive/WebIDE https://developer.mozilla.org/en-US/docs/Archive/WebIDE