Support passing null/false or a function to do nothing

[exogen]

Since React has a requirement that hooks be called unconditionally, I find that it sometimes causes hooks to need to support somewhat less elegant APIs than what would be ideal. This is one of those cases:

Since you can't call hooks conditionally, it's helpful to add support for passing a special value to the hook like false, or possibly via a function like () => someCondition ? breakpoint : false to make it do nothing until our condition is met. So in use-media's case it would not set up a matchMedia observer.

AFAIK this is the only way to work around the no-conditional requirement besides moving the hook usage into its own component and conditionally rendering that (not always possible depending on what you're doing).

Any thoughts about supporting that?