feat(Switch): support number type of size prop (#4913)

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

@@ -5,3 +5,9 @@ exports[`inactive-color prop 1`] = `
   <div class="van-switch__node"></div>
 </div>
 `;
+
+exports[`size prop 1`] = `
+<div role="switch" aria-checked="false" class="van-switch" style="font-size: 20px;">
+  <div class="van-switch__node"></div>
+</div>
+`;

src/switch/test/index.spec.js

@@ -72,3 +72,13 @@ test('inactive-color prop', () => {
 
   expect(wrapper).toMatchSnapshot();
 });
+
+test('size prop', () => {
+  const wrapper = mount(Switch, {
+    propsData: {
+      size: 20
+    }
+  });
+
+  expect(wrapper).toMatchSnapshot();
+});