Code styling

As of now, the code is very verbose and easy to read but I'm wondering if we can optimize readability by tweaking some code styles and namings to prevent double negatives.

For example, the following code...
```javascript
let unsupported;

const useSaveData = (initialSaveDataStatus = null) => {
if ('connection' in navigator && 'saveData' in navigator.connection) {
unsupported = false;
} else {
unsupported = true;
}

return {
unsupported,
saveData: unsupported
? initialSaveDataStatus
: navigator.connection.saveData === true
};
};

export { useSaveData };
```

could become...

```javascript
const useSaveData = (initialSaveDataStatus = null) => {
const supported = ('connection' in navigator && 'saveData' in navigator.connection)

return {
unsupported: !supported,
saveData: supported
? navigator.connection.saveData === true
: initialSaveDataStatus
};
};

export { useSaveData };
```

maybe even use a `supported` property in the return value, I'm not sure if it's deliberate that we use negative naming for this.