refactor(frontend): Reactivityで型を明示するように (#12791)

* refactor(frontend): Reactivityで型を明示するように

* fix: プロパティの参照が誤っているのを修正

* fix: 初期化の値を空配列に書き換えていた部分をnullに置き換え

packages/frontend/src/pages/explore.roles.vue

@@ -13,10 +13,11 @@ SPDX-License-Identifier: AGPL-3.0-only
 
 <script lang="ts" setup>
 import { ref } from 'vue';
+import * as Misskey from 'misskey-js';
 import MkRolePreview from '@/components/MkRolePreview.vue';
 import * as os from '@/os.js';
 
-const roles = ref();
+const roles = ref<Misskey.entities.Role[] | null>(null);
 
 os.api('roles/list').then(res => {
 	roles.value = res.filter(x => x.target === 'manual').sort((a, b) => b.displayOrder - a.displayOrder);