Add poster image attribute to embed styles

Problem/Motivation

This is a bug report / feature request. I don't see a poster image defined as an attribute of the tag on the 1.0.14 branch using the “Video without player” embed style. If I use the "Inline player without download (inline_view)" embed style, it is present.

The poster image is important to display while the video loads so that users know content exists, especially on slower connections, and in the case of background video, for some mobile device versions that do not display autoplaying video. There is a feature request ✨ Add embed code option allowing to autoplay DAM videos Active open for adding background video as an embed style to the module.

Proposed resolution

Add the poster image to the tag returned by all embed styles. You may also want to include an “Aquia DAM Image poster image” image style in the module. Our poster image style is 1280x720 in 3:2 aspect ratio. Thank you!