Feature request: Second parameter for atomFamily passed to default function

First of all, thank you guys for an awesome library!

I checked the latest version (0.0.8) and found your utilities atomFamily and selectorFamily very useful, but currently limited.

From your example default value for an atom in atomFamily may be parameterized:

const myAtomFamily = atomFamily({
  key: ‘MyAtom’,
  default: param => defaultBasedOnParam(param),
});

const myAtom = atomFamily(myAtomKey);

In case above myAtomKey is responsible for both: atom key and it’s default value. This behaviour makes atomFamily very limited. What if we add additional parameter to the function which is returned from atomFamily and simply pass this additional parameter to default function?

const myAtomFamily = atomFamily({
  key: ‘MyAtom’,
  default: (key, params) => defaultBasedOnKeyAndParams(key, params),
});

const myAtom = atomFamily(myAtomKey, myAtomSettings);

Now, we may (or may not) pass additional parameters to create atoms with custom default values and this addition will make atomFamily more useful. Same additional parameter should be added to selectorFamily as well:

const myGenericNumberState = atomFamily({
  key: 'MyNumbers',
  default: (key, defaultValue) => defaultValue,
});

const myGenericMultipliedState = selectorFamily({
  key: 'MyMultipliedNumbers',
  get: (key, multiplier) => ({get}) => {
    return get(myGenericNumberState(key)) * multiplier;
  },
  set: (key, multiplier) => ({set}, newValue) => {
    set(myGenericNumberState(key), newValue / multiplier);
  },
});

const xAtom = myGenericNumberState('x', 2); // creates x atom with default value 2
const yAtom = myGenericNumberState('y', 3); // creates y atom with default value 3

const x = myGenericMultipliedState('x', 5); // creates selector which multiplies x atom value by 5
const y = myGenericMultipliedState('y', 10); // creates selector which multiplies y atom value by 10

[drarmstr]

Example usage of a parameter used for a default might look something like this:

const fieldState = evaluatingAtomFamily({
  key: 'MyState',
  get: (field, defaultValue) => ({get}, fieldValue) => fieldValue ?? defaultValue,
});


const x = useRecoilValue(fieldState('email', '[e-mail]'));    

[drarmstr]

The evaluatingAtomFamily example above provides a way to use dynamic call-site-specific defaults for an atom family.