[Toggle group] Component review

[aweell]

Toggle component review

Changes on the specs can be found on: Toggle group documentation draft

Updated component specs

• Add toggle group container element
• Review button element border-radius (from 0px to 0.25rem / 4px)
• Add the possibility to have label and icon simultaneously
• Introduce a 0.25rem / 4px gutter between toggle buttons
• Add component label and helper text

Any fixes needed in the component documentation can be submitted to the component review PR