Fix compile erros

Author: jcs090218

src/components/EBanner.js

@@ -7,7 +7,7 @@
  *                   Copyright © 2022 by Shen, Jen-Chieh $
  */
 import React from 'react';
-import { Container, Button } from 'react-bootstrap';
+import { Button } from 'react-bootstrap';
 
 import banner from '../etc/sink_white.png';
 
@@ -21,7 +21,7 @@ class Ebanner extends React.Component {
       <>
         <div className="text-center">
           <div>
-            <img src= { banner }/>
+            <img src= { banner } alt="banner" />
           </div>
           <br/>
           <div className="text-info h5">

src/components/EFooter.js

@@ -7,7 +7,6 @@
  *                   Copyright © 2022 by Shen, Jen-Chieh $
  */
 import React from 'react';
-import { Container } from 'react-bootstrap';
 
 class EFooter extends React.Component {
   state = {};

src/components/ENavbar.js

@@ -11,7 +11,6 @@ import { Container, Navbar, Nav } from 'react-bootstrap';
 
 import { SiGithub } from 'react-icons/si';
 import { BsNewspaper } from 'react-icons/bs';
-import { BsQuestion } from 'react-icons/bs';
 import { FaQuestion } from 'react-icons/fa';
 import { GiLaurelsTrophy } from 'react-icons/gi';