Make the *picker_selector* keyboard accessible

[carlhaman]

You wanted some feedback on accessibillity.

If the picker_selector divs were to have role="button" and tabindex="0" they would be keyboard focusable. Then keydown eventhandlers for arrowkeys could move them.

[Sphinxxxx]

Thanks, will keep that in mind! (Pull request welcome)

[masi]

role="button" has nothing to do with being focusable: tabindex="0" is enough.

If you use role="button" you tell assistive technologies that the element acts like a button, ie acts on mouse click, space and enter. Anyway the picker_selector is a slider, not a button.

I suggest to implement this pattern:
https://www.w3.org/TR/wai-aria-practices/#slider

Naturally you don't need to worry much about screen readers, but the keyboard actions are reasonable. If you opt to use role=slider make sure to add all other attributes required by the pattern. If not it is better to use no role at all.