Confusing error when passing non-function to useMemo

[Example](https://codesandbox.io/s/boring-albattani-grhhp). When passing something like an object to `useMemo` the error isn't very helpful. ``` TypeError: nextCreate is not a function at mountMemo (https://grhhp.csb.app/node_modules/react-dom/cjs/react-dom.development.js:13459:19) ... ``` Most developers wont know what `nextCreate` is, and passing an object to `useMemo` doesn't seem _obviously_ wrong at first. We could add a `typeof` check that throws a better error, but maybe that's too much overhead? At the very least we could add a DEV warning with more helpful guidance.