API get functions: get_<response_list>_by_<param>

[farid002]

Add respective functions in api.py file into APIClass, with a meaningful and single-naming convention:
if a function is generic (takes only querystring parameter), no need for _by_param ---> i.e.: get_fixtures(querystring={"fixture": "2156"})
if a function is not generic and returns based on some parameters, then with _by_param ----> get_fixtures_by_fixture_id(fixture_id)

• Write at least: generic functions for all the endpoints existing on https://rapidapi.com/api-sports/api/api-football/
• Write necessary specific functions as well.
• Try to obey alphabetic order for function names and naming convention