feat: add examples: form-upload (#5955)

* feat: add examples: form-upload

* fix: upload: accept and label

* fix: upload: 设置表单值、图片预览

apps/backend-mock/api/upload.ts

@@ -0,0 +1,13 @@
+import { verifyAccessToken } from '~/utils/jwt-utils';
+import { unAuthorizedResponse } from '~/utils/response';
+
+export default eventHandler((event) => {
+  const userinfo = verifyAccessToken(event);
+  if (!userinfo) {
+    return unAuthorizedResponse(event);
+  }
+  return useResponseSuccess({
+    url: 'https://unpkg.com/@vbenjs/static-source@0.1.7/source/logo-v1.webp',
+  });
+  // return useResponseError("test")
+});