add redux.dev course callouts

Author: lynnandtonic

website/src/css/custom.css

@@ -280,3 +280,9 @@ details.detailed-explanation p {
   fill: black;
   stroke: black;
 }
+
+/* course callout on home page */
+.course-callout.home-mid {
+  max-width: 900px;
+  margin: 1rem auto 2rem;
+}

website/src/pages/index.js

@@ -180,6 +180,11 @@ function Home() {
             </div>
           </section>
         )}
+        <section className="course-callout home-mid">
+          <a href="https://redux.dev">
+            <img src="/img/course-callout-mid.svg" alt="Redux.dev - a new course by Mark Erikson + ui.dev - Learn more" />
+          </a>
+        </section>
         {otherLibraries && otherLibraries.length && (
           <section className={styles.features}>
             <div className="container">