`effects` keyword to describe side-effects

[ericelliott]

A way to describe side-effects in prose for documentation purposes, e.g.:

log(value) => Void, effects( log to console )

You can spread the description over multiple lines:

log(value) => Void, effects(
  log to console,
  POST to logging server
)

[timkendall]

This would be spicy 🌶