Closed Captioning

**Is your feature request related to a problem? Please describe.**
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

This feature request-related "problem" would be in terms of accessibility.

**Describe the solution you'd like**
A clear and concise description of what you want to happen.

I would like to be able to use standard caption files to provide closed captioning for the user. The idea would include a basic UI component: a CC button to toggle captions on/off, if available. Otherwise, the CC button would either not be displayed or disabled.

A container to display captions of course, with some default positioning properties top, left, bottom, and right (in relation to the player controls). As well as the typical color theme options.

The issue names no files, tests, or entry points. Start by locating the native-audio player implementation and determine how standard caption files, the CC toggle, caption positioning, and color themes would fit its supported platforms. Done should include documented behavior for available and unavailable captions, but the issue does not define the file formats or exact UI requirements.

Written by the indexing model from the issue text.