misc: fix JS errors

website/src/components/CarbonAd/index.js

@@ -33,7 +33,7 @@ export default React.memo(() => {
   useEffect(() => {
     const interval = setInterval(() => {
       [...ref.current.children].forEach((child) => {
-        if (child.id.startsWith('carbonads_')) {
+        if (child && child.id && child.id.startsWith('carbonads_')) {
           ref.current.removeChild(child);
         }
       });

website/src/css/custom.css

@@ -40,6 +40,8 @@ html[data-theme='dark'] {
   --ifm-color-primary-light: #ffb01a;
   --ifm-color-primary-lighter: #ffb426;
   --ifm-color-primary-lightest: #ffc14d;
+
+  --ifm-footer-padding-vertical: 3rem;
 }
 
 .footer__links {

website/src/theme/TOC/index.js

@@ -27,14 +27,14 @@ function TOC({className, ...props}) {
               href="https://twitter.com/techinterviewhb"
               target="_blank"
               rel="noopener noreferrer"
-              class="navbar-icon navbar-icon-twitter"
+              className="navbar-icon navbar-icon-twitter"
               aria-label="Twitter"
             />
             <a
               href="https://www.facebook.com/techinterviewhandbook"
               target="_blank"
               rel="noopener noreferrer"
-              class="navbar-icon navbar-icon-facebook"
+              className="navbar-icon navbar-icon-facebook"
               aria-label="Facebook page"
             />
           </div>