Fixed color of card symbol in solved state

Before the --fg-1 var was not being set in the solved state, leading to it having bad contrast and looking ugly in the solved state.

Author: CarsonGH

apps/svelte.dev/content/tutorial/01-svelte/07-classes-and-styles/02-styles/+assets/app-b/src/lib/App.svelte

@@ -10,6 +10,7 @@
 		style:--bg-1="palegoldenrod"
 		style:--bg-2="black"
 		style:--bg-3="goldenrod"
+		style:--fg-1="black"
 		onclick={() => flipped = !flipped}
 	>
 		<div class="front">