scale (new) icons to fit available size
scale (new) icons to fit available size

fixes https://github.com/vector-im/riot-web/issues/11399

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