fix: carousel max-width same as rest of page

The carousel expanded to the maximum width available, which is not
suitable for the webstie running on wide screens. That has been
adjusted and now has the same `max-width` as the rest of components of
the website.

docs/www/src/components/HomepageCarousel/styles.module.css

@@ -7,6 +7,8 @@
 
 .container {
   padding-top: 68px;
+  max-width: var(--ifm-container-width-xl);
+  margin: auto;
 }
 
 .title {