feat(Image): add error-icon prop (#5470)

src/image/test/__snapshots__/index.spec.js.snap

@@ -1,5 +1,12 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`error-icon prop 1`] = `
+<div class="van-image">
+  <div class="van-image__error"><i class="van-icon van-icon-error van-image__error-icon">
+      <!----></i></div>
+</div>
+`;
+
 exports[`lazy load 1`] = `
 <div class="van-image"><img class="van-image__img">
   <div class="van-image__loading"><i class="van-icon van-icon-photo-o van-image__loading-icon">

src/image/test/index.spec.js

@@ -125,6 +125,19 @@ test('show-error prop', () => {
   expect(wrapper).toMatchSnapshot();
 });
 
+test('error-icon prop', () => {
+  const wrapper = mount(Image, {
+    propsData: {
+      errorIcon: 'error',
+      src: 'https://img.yzcdn.cn/vant/cat.jpeg'
+    }
+  });
+
+  wrapper.find('img').trigger('error');
+
+  expect(wrapper).toMatchSnapshot();
+});
+
 test('loading-icon prop', () => {
   const wrapper = mount(Image, {
     propsData: {