[A11Y] Video Block - Videos not playable via screen-reader/tab focus

[Molochem]

Describe the bug
When Inspecting Video-Blocks, I noticed that the Thumbnail doesnt have an aria-label. This makes Screenreaders pretty much ignore the Video Block.

To Reproduce
Inspect the Video Block
or
Use a Screenreader and Tab through the Site

Expected behavior
The Video-Block should trigger the Screenreader / Have a descriptive aria-label

Screenshots
Inspector

Currently working on a fix

[jackahl]

We should put the play button as real button, that is selectable as a button, so screenreaders can interact.