[breaking change] rebuild style struct (#2021)

packages/uploader/demo/index.vue

@@ -43,7 +43,7 @@ export default {
 };
 </script>
 
-<style lang="postcss">
+<style lang="less">
 .demo-uploader {
   &-container {
     padding: 10px 20px;

packages/uploader/index.less

@@ -0,0 +1,22 @@
+@import '../style/var';
+
+.van-uploader {
+  position: relative;
+  display: inline-block;
+
+  &__input {
+    position: absolute;
+    top: 0;
+    right: 0;
+    bottom: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+    opacity: 0;
+    cursor: pointer;
+  }
+
+  input[type="file"]::-webkit-file-upload-button {
+    cursor: pointer;
+  }
+}