feat: add store.js && localStorage persist.

src/App.svelte

 <script>
+  import { onMount } from 'svelte';
+  import { _theme } from './stores';
   /**主题*/
   const themes = [
     'light',
@@ -70,9 +72,19 @@
       }
     }
   ];
+
+  onMount(() => {
+    // 1. 读取 localstorage
+    // -- 1.1. 读取 theme
+    document.documentElement.setAttribute('data-theme', $_theme);
+
+    // 2. 检测 darkreader 是否开启
+    const has_darkreader = document.querySelector('.darkreader');
+    if (has_darkreader) toast.push('检测到 dark reader, 建议关闭当前网站的 darkreader, 可点击导航栏的主题更改相应的主题', { initial: 0 });
+  });
 </script>
 
-<!-- <div class="top">决斗编年史</div> -->
+<!-- ----------------------------------------------- DOM ----------------------------------------------- -->
 
 <!-- 导航栏 -->
 <div class="drawer">
@@ -109,7 +121,8 @@
                     <button
                       data-theme={theme}
                       on:click={() => {
-                        document.body.parentElement.setAttribute('data-theme', theme);
+                        document.documentElement.setAttribute('data-theme', theme);
+                        $_theme = theme;
                         console.log('切换主题:\t', theme);
                       }}
                       class="rounded my-1 flex justify-between items-center"

src/stores/index.js

+import { writable } from 'svelte/store';
+
+// ----------------------------------------------------------------
+// localstorage 持久化处理 -------------------------------------
+/**localstorage 里存储字段对象的 key 名称*/
+const persistName = 'Kesa:rrpg_link';
+
+/** localstorage 数据持久化 svelte stores 函数
+ * @param {*} key 在 localstorage 存储对象里的 key 值
+ * @param {*} startValue 初始化默认值
+ * @returns svelte stores 对象
+ */
+function persistStore(key, startValue) {
+  // 判断 localstorage 中有无存储字段对象
+  if (!localStorage.getItem(persistName)) localStorage.setItem(persistName, "{}");
+
+  // 有 ls 中的值就挂载, 没有就从默认值创建, 并根据值注册 svelte store 初始化对象
+  const savedValue = JSON.parse(localStorage.getItem(persistName))[key];
+  const initialValue = savedValue ?? startValue;
+  const store = writable(initialValue);
+
+  // 对 svelte store 对象进行订阅以取得全局变化调用
+  store.subscribe(value => {
+    const data = JSON.parse(localStorage.getItem(persistName)) ?? {};
+    data[key] = value;
+    localStorage.setItem(persistName, JSON.stringify(data));
+  });
+
+  // FIXME: 对旧版本词条的处理, 过几个月也许可以去掉这个玩意儿, 减少损害其他东西的可能性
+  if (localStorage.getItem(key)) localStorage.removeItem(key)
+
+  return store;
+}
+
+// 变量 -------------------------------------
+/** 主题 */
+export const _theme = persistStore('_theme', "light");
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