UCL 39 - Icons

[Brookeruu]

• Adds new ariaHidden prop
• If ariaHidden prop is true, aria-hidden and focusable attributes are added
• Updated Button Icon example with new prop
• Added Link Icon example with new prop
• Checks for missing aria attributes (aria-label, aria-hidden, focusable (IE specific))
• Updates CSS width for links and buttons to fit only the icon -Updates aria-label example text