adding just the styling for header update

stylesheets/headings.scss

@@ -1,19 +1,18 @@
 h1,
 h2,
-h3,
-h4 {
+h3 {
   a {
     color: var(--color-auto-gray-9);
   }
 }
 
-// all h3 headers that are links should be blue-500
-h3 a {
+// all h2 headers that are links should be blue-500
+h2 a {
   color: var(--color-auto-blue-5);
 }
 
 // ... except those on each product's toc
-.product-landing h3 a {
+.product-landing h2 a {
   color: var(--color-auto-gray-9);
 }
 
@@ -22,12 +21,26 @@ h3 a {
   h2,
   h3,
   h4,
-  h5,
-  h6 {
+  h5 {
     font-family: $font-mktg;
     font-weight: $font-weight-semibold;
     padding-top: $spacer-3;
   }
+  h2 {
+    font-size: 1.25em;
+    border-bottom: none;
+  }
+  h3 {
+    font-size: 1em;
+  }
+
+  h4 {
+    font-size: 0.875em;
+  }
+
+  h5 {
+    font-size: 0.85em;
+  }
 }
 
 // needs specificity to override