add start button

- new stage will load previous stored data at first

app/src/components/game/StartButton.vue

@@ -0,0 +1,51 @@
+<script setup lang="ts">
+import { useToast } from 'vue-toastification'
+import { ref } from 'vue'
+import { init } from '../../store/session'
+import { LoadQuestError, LoadSessionError } from '../../utils/errors'
+
+const props = defineProps({
+  questId: {
+    type: String,
+    required: true,
+  },
+})
+
+const toast = useToast()
+const showCover = ref(true)
+const startSession = async () => {
+  showCover.value = false
+  try {
+    await init(props.questId)
+  } catch (err: any) {
+    if (err instanceof LoadQuestError) {
+      toast.error(`無法讀取關卡: ${err.questId}，請確認網頁連結。`)
+      return
+    }
+    if (err instanceof LoadSessionError) {
+      toast.error(`無法建立工作階段: ${err.questId}，請重新登入再試一次。`)
+      return
+    }
+    console.error(err)
+    toast.error(err.message)
+  }
+}
+</script>
+<template>
+  <div
+    v-if="showCover"
+    class="bg-bg-secondary h-full w-1/2 fixed bg-opacity-50 flex justify-center items-center"
+  >
+    <button
+      id="start"
+      class="bg-bg-secondary rounded-lg p-3"
+      @click="startSession"
+    >
+      <font-awesome-icon
+        :icon="['fas', 'play']"
+        class="text-text-primary h-full px-3"
+      />
+      <p class="text-text-primary inline ml-1 md:flex">開始</p>
+    </button>
+  </div>
+</template>