Start using the new modal component

This attempts to converge all our modals on the new modal component while changing their designs as little as possible. This should reduce the bundle size a bit and make the app generally feel like it's converging on the new designs, even though individual modals still remain to be revamped.

src/room/ShareModal.module.css

@@ -14,10 +14,6 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-.inviteModal {
-  max-width: 413px;
-}
-
 .copyButton {
   width: 100%;
 }