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/components/UsernameChooser.js b/client/src/components/UsernameChooser.js
index 0061701..57fa242 100644
--- a/client/src/components/UsernameChooser.js
+++ b/client/src/components/UsernameChooser.js
@@ -1,7 +1,8 @@
+import { SearchRounded } from '@mui/icons-material';
+import { InputAdornment, TextField } from '@mui/material';
 import { useEffect, useState } from 'react';
 import usePromise from 'react-fetch-hook/usePromise';
-import { InputAdornment, TextField } from '@mui/material';
-import { SearchRounded } from '@mui/icons-material';
+
 import authManager from '../AuthManager';
 
 const isInputValid = (input) => input && input.length > 2;