parse(): thow an error when parsing is unsuccessful

It would be very practical, if parse would throw an error if it was not successful in parsing a color.

```js
try {
const color = culori.parse('something');
console.log({color}); // {{ color: undefined }}
} catch (error) {
console.error(error);
}
```

The only way I can do this now is check for `undefined`.
I'd find it very practical to get something like:

```js
throw new Error(
`parse() must be an object or a valid color string but \`${arguments}\` were given.`
);
```