style(common): add grid layout for solution columns in navigation

public/themes/dist_static/static/css/common.css

@@ -1534,6 +1534,7 @@ body {
 }
 html[lang="en"] .nav-mega__cols--solution {
   gap: 2rem;
+  grid-template-columns: repeat(4, minmax(0, 1fr));
 }.nav-mega__col {
   display: flex;
   flex-direction: column;