Instructions for using debuggers outside futurecoder

After introducing each debugger, we should maybe point out at the end that users can still use these tools outside of futurecoder. For example:

> You can also use snoop outside futurecoder, e.g. if you're writing and running code on your own computer and editor. Assuming you have Python and `pip` set up, run `pip install snoop` and follow the instructions [here](https://github.com/alexmojaki/snoop).

Many users would not know what to do with this, but maybe some will remember that this was mentioned when they've moved on from futurecoder but miss the debuggers. They can come back and check or do some googling instead of thinking it has to be built into the IDE.

This is based on a discussion with @matan-h