1.2.3 Video element visual content has accessible alternative - composite check

494 - examples
- Fail 1
- Fail 2
- Fail 3
- Fail 4
- Pass 1
- Pass 2
- Pass 3
- Inapplicable 1
- Inapplicable 2
- Shadow 1
- Shadow 2
- Shadow 3
- Shadow 4
- Shadow 5