Add docs for compound :global selector

site/content/docs/01-component-format.md

@@ -277,6 +277,12 @@ To apply styles to a selector globally, use the `:global(...)` modifier.
 			 to this component */
 		color: goldenrod;
 	}
+
+	p:global(.red) {
+		/* this will apply to <p> elements belonging to this 
+			 component that have the class "red" dynamically
+			 applied (e.g. via node.classList.add) */
+	}
 </style>
 ```