Clarify external links on startpage

src/components/HomepageFeatures/index.js

@@ -1,5 +1,6 @@
 import React from 'react';
 import clsx from 'clsx';
+import IconExternalLink from '@theme/Icon/ExternalLink';
 import styles from './styles.module.css';
 
 const FeatureList = [
@@ -37,7 +38,7 @@ function Feature({title, description, link}) {
     <div className={clsx('col col--4')}>
       <div className="text--center padding-horiz--md">
         <a href={link} target='_blank' style={{color: 'var(--ifm-font-color-base)'}}>
-          <h3>{title}</h3>
+          <h3>{title}<IconExternalLink/></h3>
           <p>{description}</p>
         </a>
       </div>