Bug fix video player controls a11y

Proper WAI-ARIA  attributes were added to all the elements that can receive focus via the keyboard. Their role, name, and state can be fetched by a screen reader.

This is what is the output when using Voice Over:

PROGRESS CONTROL:

Announces itself as:

'0 seconds video position slider list 4 items'

When horizontal keys are used, speaks out the position of the video in 'hour:minute:second' format.


PLAY/PAUSE CONTROL:

Announces itself as:

'Play (or Pause) button list 2 items level 2'


SPEED CONTROL:

Announces itself as:
'SPEED 1.0x speeds button'

and the menu items as:

'link 1.50x'


VOLUME CONTROL:

Announces itself as:

'Volume button'

The slider that appears announces itself as:

'very low volume slider"

and when the up/down arrows are used, goes through:

'silent', 'very low', 'low', 'average', 'loud', 'very loud', 'maximum'


LAST THREE CONTROLS:

They announce themselves as:

'Fill browser button'
'HD button'
'Turn off caption button'