Implement Cookies support

The same way it is implemented in Zendriver, reimplement Browser.cookies and CookieJar:

```python
class Browser:

    @property
    def cookies(self) -> CookieJar:
        if not self._cookies:
            self._cookies = CookieJar(self)
        return self._cookies

class CookieJar:

    # See Zendriver for implementation
```
