use css fadein anim on modal windows

src/components/modals/index.js

@@ -5,6 +5,7 @@ import { CSSTransition } from 'react-transition-group';
 
 import styled from 'styled-components';
 import colors from 'config/colors';
+import { FADE_IN } from 'config/animations';
 
 import { UI } from 'trezor-connect';
 import * as MODAL from 'actions/constants/modal';
@@ -31,6 +32,7 @@ import Stellar from 'components/modals/external/Stellar';
 
 import type { Props } from './Container';
 
+// TODO: animation not working
 const Fade = (props: { children: React.Node}) => (
     <CSSTransition
         {...props}
@@ -53,6 +55,7 @@ const ModalContainer = styled.div`
     align-items: center;
     overflow: auto;
     padding: 20px;
+    animation: ${FADE_IN} 0.3s;
 `;
 
 const ModalWindow = styled.div`