Add option to disable video download on mixed content sites

[virtualzx-nad]

Original issue: RipMeApp#2098

Problem:
When ripping from content aggregators like Reddit that have both images and videos, users should have the option to skip video downloads.

Requirements:

1. Add a new configuration option to disable video downloads
2. Implement the skip logic in relevant rippers
3. Update documentation
4. Add tests for the new functionality

Difficulty: Beginner-friendly
Type: Enhancement