aper-toggle-button` provides a ON/OFF switch that user can toggle the state
by tapping or by dragging the swtich.

Example:

    <paper-toggle-button></paper-toggle-button>

Styling toggle button:

To change the toggle color:

    paper-toggle-button::shadow .toggle {
      background-color: #9c27b0;
    }

To change the ink color:
    
    paper-toggle-button::shadow .toggle-ink {
      color: #009688;
    }

To change the checked toggle color:

    paper-toggle-button::shadow [checked] .toggle {
      bac