fix: Uploade 组件无法预览图片 (#2822)

Author: Madq92

src/packages/uploader/uploader.scss

@@ -178,7 +178,8 @@
         display: flex;
         justify-content: center;
         align-items: center;
-        height: 100%;
+        width: var(--nutui-uploader-image-width, 100px);
+        height: var(--nutui-uploader-image-height, 100px);
         position: initial;
         border-radius: $uploader-image-border-radius;
       }