feat(join): hide join button if already on a room

app/src/lib/join.svelte

@@ -21,6 +21,7 @@
 >
 	<div class="space-y-4 max-w-[70%]">
 		{#if roomCode}
+		<div class="text-center text-lg text-primary-content">Share this code with your opponent to play</div>
 			<div class="space-x-2 flex flex-row justify-center items-center">
 				<div
 					class="text-3xl font-bold tracking-widest text-secondary-content font-mono bg-secondary py-3 rounded-full px-12"
@@ -40,6 +41,7 @@
 				Create Room
 			</button>
 		{/if}
+		{#if !roomCode}
 			<div class="text-center text-lg text-primary-content">OR</div>
 			<div class="space-y-2">
 				<input
@@ -56,5 +58,6 @@
 					Join Room
 				</button>
 			</div>
+		{/if}
 	</div>
 </div>