Tutorial/max cut

[ahao27]

Changes

1. Added a tutorial notebook file, "maxcut.ipynb," under the docs/tutorial/.
2. Fixed the index.md file.
3. Updated the _toc.yml file.

Description

This tutorial demonstrates how to solve the Max-Cut problem by using QAOA method, Qamoile and Jijmodleing.

[ahao27]

change after 4b32adf

The section (last cell) comparing different $p $-layers and frequencies has been removed to align with other tutorials and maintain a focus on solving the problem.

[Jacomichi]

LGTM