Sort imports from all files

Add "prettier" script in `package.json` to check if all files are
compliant.

Sort all imports and format all files by running `npm run lint -- --fix`
followed by `npm run prettier -- --write`.

Gitlab #29

Change-Id: Id80402d1344c3bc611f66a46cffeee5f2c375bd8
diff --git a/client/src/pages/accountCreation.jsx b/client/src/pages/accountCreation.jsx
index f4d3921..cd948a2 100644
--- a/client/src/pages/accountCreation.jsx
+++ b/client/src/pages/accountCreation.jsx
@@ -1,5 +1,6 @@
-import { Container, Card, CardContent, Typography, List, Avatar, Divider } from '@mui/material';
 import { DialerSipRounded, GroupOutlined, RoomRounded } from '@mui/icons-material';
+import { Avatar, Card, CardContent, Container, Divider, List, Typography } from '@mui/material';
+
 import ListItemLink from '../components/ListItemLink';
 
 export default function AccountCreationDialog(props) {