EventTile: add classes to indicate verifiedness
EventTile: add classes to indicate verifiedness

Add a couple of CSS classes to event tiles to reflect whether encrypted events
have been verified or not.

matrix-org/matrix-react-sdk,aperezdc/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,aperezdc/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,aperezdc/matrix-react-sdk,matrix-org/matrix-react-sdk,aperezdc/matrix-react-sdk