Update docs for LLMs and Overview

[Dev-Khant]

Description

Update Docs:

• Add docs on how to use Mistral and Azure AI models.
• Explaining how Mem0 works.

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• [x] Documentation update

How Has This Been Tested?

• [] Unit Test
• [ ] Test Script (please provide)

Checklist:

• [ ] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules
• [ ] I have checked my code and corrected any misspellings

Maintainer Checklist

• [ ] closes #xxxx (Replace xxxx with the GitHub issue number)
• [ ] Made sure Checks passed

[Dev-Khant]

@deshraj Comments are resolved.