style(alert): fix alert border color

修复Alert组件的默认边框颜色不正确的问题

src/design/theme.less

@@ -6,6 +6,21 @@ html[data-theme='light'] {
   .text-secondary {
     color: rgba(0, 0, 0, 0.45);
   }
+
+  .ant-alert-success {
+    background-color: #f6ffed;
+    border: 1px solid #b7eb8f;
+  }
+
+  .ant-alert-error {
+    background-color: #fff2f0;
+    border: 1px solid #ffccc7;
+  }
+
+  .ant-alert-warning {
+    background-color: #fffbe6;
+    border: 1px solid #ffe58f;
+  }
 }
 
 [data-theme='dark'] {