Testing for Text Track Audio Descriptions

[elynema]

Description

Test behavior of text track audio descriptions in Ramp to make sure they are meeting user needs.

Done Looks Like

• AD functionality is visible to users in Ramp.
• When the user turns AD functionality on, the .vtt file should be read aloud to the user as the video plays.
• Screenreaders can auto-detect the text track .vtt and automatically read it aloud without the user taking specific action beyond starting playback
• Test what happens in Ramp when captions are turned on by default. Is audio description still available to the user?
• Test behavior of audio description text tracks in iOS native player. Do they work?

[cjcolvar]

Part of avalonmediasystem/avalon#6397