fix: 修复低版本浏览器不兼容 (#301)

* feat: add polyfills for Array.prototype.at and String.prototype.at methods

* chore: bump version to v0.9.51

package.json

@@ -1,6 +1,6 @@
 {
   "name": "vocechat-web",
-  "version": "0.9.50",
+  "version": "0.9.51",
   "homepage": "https://voce.chat",
   "dependencies": {
     "@metamask/onboarding": "^1.0.1",

src/libs/polyfills.js

@@ -18,3 +18,26 @@ if (!isSupported) {
 }
 // hasown API
 "hasOwn" in Object || (Object.hasOwn = Object.call.bind(Object.hasOwnProperty));
+
+// Array.prototype.at() and String.prototype.at() polyfill
+if (!Array.prototype.at) {
+  Array.prototype.at = function (index) {
+    const len = this.length;
+    const relativeIndex = index >= 0 ? index : len + index;
+    if (relativeIndex < 0 || relativeIndex >= len) {
+      return undefined;
+    }
+    return this[relativeIndex];
+  };
+}
+
+if (!String.prototype.at) {
+  String.prototype.at = function (index) {
+    const len = this.length;
+    const relativeIndex = index >= 0 ? index : len + index;
+    if (relativeIndex < 0 || relativeIndex >= len) {
+      return undefined;
+    }
+    return this[relativeIndex];
+  };
+}