fix(docs-infra): size footer links to appropriate size for SEO (#35098)

Footer links did not have enough space between them, so lighthouse was
reporting that tap targets are not appropriately sized. Added the
required 8px space between links.

Also updated the margin of group headers accordingly.

Fixes #34901

PR Close #35098

aio/src/styles/1-layouts/_footer.scss

@@ -40,7 +40,7 @@ footer {
     @include font-size(16);
     text-transform: uppercase;
     font-weight: 400;
-    margin: 0 0 16px;
+    margin: 8px 0 12px;
     color: $white;
   }
   p {
@@ -69,7 +69,7 @@ footer {
 
       li {
         list-style-type: none;
-        padding: 0px;
+        padding: 4px 0;
         text-align: left;
       }
     }