This awesome! I just created a Julia Debugger playground on Repl.it: https://repl.it/@amasad/julia-debug (it's a bit slow to start but then runs smoothly)
Here is a quick screencast: https://imgur.com/a/PXTRgHp
Here is a quick screencast: https://imgur.com/a/PXTRgHp
Just a quick note for the inattentive like me: you have to click the "Run" button before executing the `@enter foo(20)` command.