[Feature] Add a .markdown() function for response

[perklet]

Extract LLM-friendly markdown text from response.

Is your feature request related to a problem? Please describe.
N/A

Describe the solution you'd like

from curl_cffi import requests

r = requests.get("https://example.com/content-20240704.html")

text = r.markdown()

Describe alternatives you've considered
N/A

Additional context
Dependeices should be optional, probably with pip install curl-cffi[extra]