fix: 修复uni-id相关接口使用atob在不支持的平台导致报错的Bug

packages/uni-vue/src/uni-id-mixin.ts

+let realAtob: (b64Str: string) => string
+
+const b64 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/='
+const b64re =
+  /^(?:[A-Za-z\d+/]{4})*?(?:[A-Za-z\d+/]{2}(?:==)?|[A-Za-z\d+/]{3}=?)?$/
+
+if (typeof atob !== 'function') {
+  realAtob = function (str: string) {
+    str = String(str).replace(/[\t\n\f\r ]+/g, '')
+    if (!b64re.test(str)) {
+      throw new Error(
+        "Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded."
+      )
+    }
+
+    // Adding the padding if missing, for semplicity
+    str += '=='.slice(2 - (str.length & 3))
+    var bitmap
+    var result = ''
+    var r1
+    var r2
+    var i = 0
+    for (; i < str.length; ) {
+      bitmap =
+        (b64.indexOf(str.charAt(i++)) << 18) |
+        (b64.indexOf(str.charAt(i++)) << 12) |
+        ((r1 = b64.indexOf(str.charAt(i++))) << 6) |
+        (r2 = b64.indexOf(str.charAt(i++)))
+
+      result +=
+        r1 === 64
+          ? String.fromCharCode((bitmap >> 16) & 255)
+          : r2 === 64
+          ? String.fromCharCode((bitmap >> 16) & 255, (bitmap >> 8) & 255)
+          : String.fromCharCode(
+              (bitmap >> 16) & 255,
+              (bitmap >> 8) & 255,
+              bitmap & 255
+            )
+    }
+    return result
+  }
+} else {
+  // 注意atob只能在全局对象上调用，例如：`const Base64 = {atob};Base64.atob('xxxx')`是错误的用法
+  realAtob = atob
+}
+
 function b64DecodeUnicode(str: string): string {
   return decodeURIComponent(
-    atob(str)
+    realAtob(str)
       .split('')
       .map(function (c) {
         return '%' + ('00' + c.charCodeAt(0).toString(16)).slice(-2)