feat: add rollover tile component

This adds a component that reveals text content when hovering, focusing, or active. It is different from the rollovers present on the eclipse.org homepage. Unlike the homepage, these do not replace the original content of the tile.

Hopefully, in the future, we could add a variant of this component which could be used on the homepage.

https://xd.adobe.com/view/55d0555c-7c69-4bcd-a7d8-a78ffa6dca76-0083/