[IO] Support dict for HTTP Basic Auth config & fix docs

[probberechts]

Kloppy supports fetching data from URLs protected with HTTP Basic Auth. Previously, the documentation stated that this requires setting the following configuration:

from kloppy.config import set_config

set_config(
    'adapters.http.basic_authentication',
    { 'user': 'JohnDoe', 'pass': 'asecretkey' }
)

However, since the configuration variable is unpacked as aiohttp.BasicAuth(*basic_authentication), the correct way to set the configuration variable was to define it as a tuple:

set_config(
    'adapters.http.basic_authentication',
    ('JohnDoe', 'asecretkey',)
)

Moreover, the keys used are incorrect, as aiohttp.BasicAuth uses "login" and "password".

I've updated the code such that 'adapters.http.basic_authentication' now accepts both a dict and a tuple, fixed the documentation, and added tests for retrieving data from URLs protected with HTTP Basic Auth.

---

• Support passing basic auth config to aiohttp.BasicAuth using keyword arguments
• Fix documentation example to use correct auth config keys
• Raise a clear KloppyError for malformed basic auth configuration
• Add tests for authenticated, unauthenticated, and invalid auth cases

Fixes #78