Add methods for joining a game.

src/components/GameCode.vue

@@ -10,15 +10,24 @@
 				id="username"
 				name="User Name"
 				v-model="username"
+				@keyup.enter.stop="$refs.gamecode.focus()"
 			>
 			<br>
 			<label for="gamecode">Game Code:</label>
 			<input
+				ref="gamecode"
 				type="text"
 				id="gamecode"
 				name="Game Code"
 				v-model="game_code"
+				@keyup.enter.stop="try_game_code"
 			>
+			<br>
+			<button
+				@click.stop="try_game_code"
+			>
+				Join Game
+			</button>
 		</div>
 	</div>
 </template>
@@ -31,7 +40,14 @@ export default {
 		game_code: ``,
 		username: ``,
 	}},
-	methods: {},
+	methods: {
+		try_game_code() {
+			if (this.game_code.length > 0) {
+				alert('The game code you have entered is invalid.');
+				this.game_code = ``;
+			}
+		},
+	},
 }
 </script>