Add support for session key file or cookie file to login

[ryanlua]

Is your feature request related to a problem?

Sometimes it is better to use a file to log into Instaloader than a username and password as evidenced by https://github.com/RyanLua/InstaWebhooks/discussions/15.

Describe the solution you'd like

Two new arguments to login with session key file or cookie file.

Describe alternatives you've considered

No response

Additional context

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[SheepyChris]

Is there any chance this will be implemented in the future? The current version ends up with errors 401 and 443 after being in use for a few hours despite checks being done every half hour.