feat(Overlay): add custom-style prop (#4572)

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

@@ -2,6 +2,8 @@
 
 exports[`class-name prop 1`] = `<div class="van-overlay my-overlay" style="z-index: 1;" name="van-fade"></div>`;
 
+exports[`custom style prop 1`] = `<div class="van-overlay" style="z-index: 1; background-color: red;" name="van-fade"></div>`;
+
 exports[`default slot 1`] = `<div class="van-overlay" style="z-index: 1; display: none;" name="van-fade">Custom Default</div>`;
 
 exports[`duration prop 1`] = `<div class="van-overlay" style="z-index: 1; animation-duration: 1s;" name="van-fade"></div>`;

src/overlay/test/index.spec.js

@@ -23,6 +23,19 @@ test('class-name prop', () => {
   expect(wrapper).toMatchSnapshot();
 });
 
+test('custom style prop', () => {
+  const wrapper = mount(Overlay, {
+    propsData: {
+      show: true,
+      customStyle: {
+        backgroundColor: 'red'
+      }
+    }
+  });
+
+  expect(wrapper).toMatchSnapshot();
+});
+
 test('duration prop', () => {
   const wrapper = mount(Overlay, {
     propsData: {