Add MediaGroup Filter

[WhiteMemory99]

Description

Add a brand new filter for media groups. Taking the latest Telegram Bot API updates into account, this filter might be quite useful for more and more people in the future.

Type of change

• Documentation (typos, code examples or any documentation update)
• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

Test Configuration:

• Operating System: Ubuntu 20.04
• Python version: 3.8.5

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• 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