Summary: - Add a close button when hovering over the component - Remove the route corresponding to it when clicking on closing Note: - This is a part of this PR: https://github.com/facebook/flipper/pull/488 Reviewed By: mweststrate Differential Revision: D20444419 fbshipit-source-id: 5ebe112c542b033a3e10ed10f23d6a04a730c657