[new feature] Uploader: add preview-size prop

packages/uploader/test/__snapshots__/index.spec.js.snap

@@ -11,6 +11,19 @@ exports[`max-count prop 1`] = `
 </div>
 `;
 
+exports[`preview-size prop 1`] = `
+<div class="van-uploader">
+  <div class="van-uploader__wrapper">
+    <div class="van-image van-uploader__preview" style="width: 30px; height: 30px;"><img src="test" class="van-image__img" style="object-fit: cover;">
+      <div class="van-image__loading"><i class="van-icon van-icon-photo-o" style="font-size: 22px;">
+          <!----></i></div>
+    </div>
+    <div class="van-uploader__upload" style="width: 30px; height: 30px;"><i class="van-icon van-icon-plus van-uploader__upload-icon">
+        <!----></i><input type="file" accept="image/*" class="van-uploader__input"></div>
+  </div>
+</div>
+`;
+
 exports[`render preview image 1`] = `
 <div class="van-uploader">
   <div class="van-uploader__wrapper">

packages/uploader/test/index.spec.js

@@ -150,3 +150,17 @@ it('max-count prop', async () => {
 
   expect(wrapper).toMatchSnapshot();
 });
+
+it('preview-size prop', async () => {
+  const wrapper = mount(Uploader, {
+    propsData: {
+      preview: true,
+      previewSize: 30
+    }
+  });
+
+  wrapper.vm.onChange(file);
+  await later();
+
+  expect(wrapper).toMatchSnapshot();
+});