Consider alternative playpen backends for remote code execution

[budziq]

Currently the support for https://play.rust-lang.org/ is hardcoded into book.js. We might be interested to support alternative ones like

Like:

• https://play.integer32.com/ for rust
• https://rust.godbolt.org/ - compiler explorer is not a playpen pe se but it's immensely useful. (Also for other languages)

Also take into consideration support for other languages:

• https://play.golang.org/
• https://code.sololearn.com/#cpp

See https://fiddles.io/ for extended list

[agauniyal]

+1 for godbolt. I would like to present wandbox as common denominator here as well.

[CjS77]

There's an easy workaround here:
mdbook init --theme

and edit book.js to point to your custom playpen/playground (Rust only, mind you)

[vanceism7]

I'm really interested in getting this feature going - Mdbook is great but it'd be nice if we could hook into other playground code editors (like purescript, haskell, etc). I don't mind trying to implement this myself, does anyone have any suggestions as a good starting point?