Add keyboard focus border for dropdown options

[Pytal]

Add keyboard focus border on dropdown options to improve accessibility similar to the examples below:

• Single-select example
• Multi-select example

Active background color

The default dropdown active background color is darkened #5897fb → #136cfb to meet minimum WCAG AA contrast ratio requirements

Before	After

Visible focus border

When keyboard navigation is detected a visible border #949494 is added around the focused dropdown option

	Screenshot
Contrast
Example

The example above uses

keyboardFocusBorder: true,

and

--vs-dropdown-option--active-bg: #f5f5f5;
--vs-dropdown-option--active-color: var(--vs-dropdown-option-color);