[css-nesting-1] add additional example for nested conditionals

Author: Adam Argyle

css-nesting-1/Overview.bs

@@ -465,6 +465,38 @@ Nesting Conditional Rules {#conditionals}
        }
      */
 
+    .foo {
+      display: grid;
+
+      @media (orientation: landscape) {
+        & { 
+          grid-auto-flow: column; 
+        }
+
+        @media (min-inline-size > 1024px) {
+          & {
+            max-inline-size: 1024px;
+          }
+        }
+      }
+    }
+
+    /* equivalent to
+       .foo { display: grid; }
+
+       @media (orientation: landscape) {
+         .foo { 
+           grid-auto-flow: column; 
+         }
+       }
+
+       @media (orientation: landscape) and (min-inline-size > 1024px) {
+         .foo { 
+           max-inline-size: 1024px;
+         }
+       }
+     */
+
     .foo {
       color: red;