Add note about putting then and else forms on separate lines in `if`

[camsaul]

I've seen code like

(if (or (something)
        (something-else))
  do-something do-something-else)

in the wild. I would like to be able to point to a style guide note about this. This doesn't apply of course to things like

(if x then else)

Where it's all on one line but if you're going to format it with multiple lines then put the then and else forms on different lines

[bbatsov]

Yeah, I agree with that suggestion. Generally I think it's fine to have both branches on the same line only for trivial (e.g. one-line conditionals).

[seancorfield]

PR welcome, at this point.

[seancorfield]

PR is still welcome :)