Add optional clear button when the select is open, to clear all items

[acetinick]

Is your feature request related to a problem? Please describe.
Looking for obvious way to clear all items of the select whilst hovering or select box is open.

Describe the solution you'd like

Add 'times' icon to bottom right, or right of the select box to allow user to clear all selections. Should be able to be done on hover and whilst the select is open

Describe alternatives you've considered

• optional flag to show this, maybe "showClear"
• should show on hover, and whilst its open

[oyejorge]

Just pushed out v1.3 with the clear_button plugin