Fix 403 error when using WooCommerce API (Python)

[Matin-B]

This pull request fixes an issue where a 403 error was returned when trying to use the WooCommerce API in Python. The issue was caused by the lack of a User-Agent header in the API requests.

To fix the issue, a User-Agent header has been added to the API requests, with the value "sample.org" (or anything else).

Changes made:

• Added a User-Agent header to the API requests with the value "sample.org".

Example usage:

from woocommerce import API

wcapi = API(
    url="http://example.com",
    consumer_key="consumer_key",
    consumer_secret="consumer_secret",
    version="v2",
    user_agent="sample.org", # Your sample user agent
)