Tooltip & popover visibility

[gfellerph]

Should we add borders to tooltips and popovers?

When a tooltip has a similar background lightness than the body, it's visibility suffers, even though there is a shadow.

Hint: upcoming palette proposal would add the possibility to define an optional border color for each palette color.

[gfellerph]

Resolution: Offer tooltips in two color vairants. One for light and one for dark mode. Adding a border is a good idea, because we can't be sure if a tooltip is displayed on a dark or light background.

[gfellerph]

Closing as will be handled in different issues