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/MessageList.js b/client/src/components/MessageList.js
index 0dc4975..0d2dc10 100644
--- a/client/src/components/MessageList.js
+++ b/client/src/components/MessageList.js
@@ -1,16 +1,17 @@
+import { Stack } from '@mui/system';
 import dayjs from 'dayjs';
-import { useMemo } from 'react';
 import dayOfYear from 'dayjs/plugin/dayOfYear';
 import isBetween from 'dayjs/plugin/isBetween';
-import { Stack } from '@mui/system';
+import { useMemo } from 'react';
+
 import {
+  MessageBubblesGroup,
   MessageCall,
   MessageDate,
   MessageInitial,
   MessageMember,
-  MessageBubblesGroup,
-  MessageTime,
   MessageMerge,
+  MessageTime,
 } from './Message';
 
 dayjs.extend(dayOfYear);