[new feature] Loading: add text-size prop

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

@@ -0,0 +1,3 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`text-size prop 1`] = `<div class="van-loading van-loading--circular"><span class="van-loading__spinner van-loading__spinner--circular" style="color: rgb(201, 201, 201);"><svg viewBox="25 25 50 50" class="van-loading__circular"><circle cx="50" cy="50" r="20" fill="none"></circle></svg></span><span class="van-loading__text" style="font-size: 20px;">Text</span></div>`;

packages/loading/test/index.spec.js

@@ -0,0 +1,15 @@
+import { mount } from '../../../test/utils';
+import Loading from '..';
+
+test('text-size prop', () => {
+  const wrapper = mount(Loading, {
+    propsData: {
+      textSize: 20
+    },
+    scopedSlots: {
+      default: () => 'Text'
+    }
+  });
+
+  expect(wrapper).toMatchSnapshot();
+});