[fn] for funcion callbacks

[cironunes]

You know, for when you need callback functions. See this gist

[chmanie]

Yeah. +1 from me. fn for anonymous functions. I use them much more often than named functions.
I actually changed [fu] to be an anonymous function and [fn] to be a named function in my fork.

[zenorocha]

Hey @chmanie, could you send a PR with this suggestion?

[cironunes]

Great! 👍