WSTEAM1-POC: Add button and signpost

[shayneahchoon]

Transcript Experiment

Overall changes

Adds signpost and mini playbutton.

Code changes

• Affects Media Loader, which affects video on newer Article, Media Article Pages.
• Guidance message will not show if the experiment is enabled.

Testing

1. List the steps used to test this PR.

Helpful Links

Add Links to useful resources related to this PR if applicable.

Coding Standards

Repository use guidelines