Added multimedia playlist and player for Python

[ali-hv]

Added a tutorial for building a multimedia playlist and player in Python, using PyQt. Added "Desktop Application" section to python's technologies.

Description

Motivation and Context

How Has This Been Tested?

Types of changes

• [x] Content Update (change which fixes an issue or updates an already existing submission)
• [ ] New Article (change which adds functionality)
• [ ] Documentation change

Checklist:

• [x] My code follows the code style of this project.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] I have made checks to ensure URLs and other resources are valid