Enhance aria labeling of play-pause button

[karendolan]

This pull is a request to enhance the Player play-pause aria labelling to make it dynamic. Similar to the Youtube aria handling.

• This pull needs the addition of language nationalization handling.
• The "ariaKeyshortcuts" config is related to a companion request to make the shortcuts info plugin listing dynamic based on active plugins, instead of a generic list.

Example of config additions for this change,

        "es.upv.paella.playPauseButton" : {
            "enabled": true,
            "order": 0,
            "tabIndex": 1,
            "ariaKeyshortcuts": "k",
            "ariaLabelPlay": "Play",
            "ariaLabelPause": "Pause"

        },