feat: 增加symbol方法

src/index.ts

@@ -18,4 +18,5 @@ export { default as isEmpty } from './isEmpty'
 export { default as isFunction } from './isFunction'
 export { default as isNuil } from './isNuil'
 export { default as isNull } from './isNull'
-export { default as isObject } from './isObject'
+export { default as isObject } from './isObject'
+export { default as isSymbol } from './isSymbol'

src/isSymbol.ts

@@ -0,0 +1,9 @@
+/**
+ * 检查一个值是否为Symbol类型。
+ * @param value 待检查的值。
+ * @returns 布尔值，表示值是否为Symbol类型。
+ */
+export default function isSymbol(value: unknown): boolean {
+  // 使用 typeof 检查值的类型是否为 'symbol'
+  return typeof value === 'symbol';
+}