Forced captions - #911

Related issue: #906

This PR enables parsing and auto-enabling of forced text tracks in VideoJS. Ramp uses a forced flag in the text-track objects it creates from the parsed information to keep track of the forced text-tracks.

One of the done looks like suggests the following,

The forced text track should be identifiable in the captions menu (different CSS, or potentially don't display to users)

Solution implemented in this work,
The forced text track in the captions menu is displayed with the forced text in the label with a tooltip. Hiding this in the captions menu will have the following implications that are not desirable,

• UX: removes the clutter but can cause confusion when captions display without an active text track even when the users have turned them off previously
• A11y: hiding the track breaks the broader 'Understandable' principle in WCAG guidelines

Additionally,

• Changes to the captions menu with longer file names,
  • File name with spaces;

- File name with underscores (without spaces); - Fix the captions handling in Safari and Chrome in iOS; remove duplicated subtitle/caption options in the captions menu

Demo:

demo-forced-captions.mov