AV: Add guidance to media placeholder image

[12]

Is your feature request related to a problem? Please describe.
We need to add guidance messages to the placeholder images for media assets.

Describe the solution you'd like
As we have the entire aresMedia block to our disposal, we know if a media asset comes with guidance messages. This means that we should easily be able to add the guidance messages to our placeholder image, with our UX spec (including the screen reader UX) in mind.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Testing notes
This will require an a11y swarm once the logic is ready/available. This will require cross-browser testing to make sure there's no overlapping UI. We will implement Cypress tests to make sure the component appears if there is a guidance message.

Dev insight: Snapshots, Cypress tests to ensure the component is visible when a video block has a guidance message.

Additional context
Guidance/Warnings: The terminology is confusing because different systems use the opposite names for each thing. We should use what Ares calls warnings.short in the field SMP calls guidance

• SMP guidance is things like This video contains swears
• SMP warnings are things like This video has no sound
• SMP warnings are a nice to have that MPV and Ares doesn't currently support.

[lizcameron]

Updated design for Guidance message from UX: https://app.zeplin.io/project/5baa564c05c2eba0d2b89568/dashboard?seid=5c59ad214e1897355941da14
Screenreader UX to follow.

[lizcameron]

Screenreader UX: https://app.zeplin.io/project/5baa564c05c2eba0d2b89568/screen/5c59ad1aa48da042125184d0

[PriyaKR]

Is the guidance just been added to canonical media player page or even on amp?