Update SessionMiddleware and TrustedHostMiddleware Documentation

[soulee-dev]

Summary

This PR updates the documentation for SessionMiddleware and TrustedHostMiddleware to reflect the current code more accurately.

Changes

1. SessionMiddleware:

• Added documentation for the path parameter which specifies the path set for the session cookie. It defaults to "/".

2. TrustedHostMiddleware:

• Added documentation for the www_redirect parameter. When set to True, this option redirects requests to non-www versions of allowed hosts to their www counterparts. This parameter defaults to True.

Checklist

• I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.

[Kludex]

Thanks! :)