Return Raw response & validation fixes

Fixed validation errors in pydantic models for:

• book
• thumbnail
• news
• web_search

Users can return raw if pydantic validation fails to not block them 🔥

from brave import Brave

query = "George Orwell, 1984"
num_results = 10

search_results = brave.search(q=query, raw=True)

@harishankar-gopalan fixed a compatability issue with Python 3.9 🚀