feat: demo of motion plugin (#5550)

添加Motion的用法例子

packages/effects/plugins/src/motion/index.ts

@@ -0,0 +1,8 @@
+export * from './types';
+
+export {
+  MotionComponent as Motion,
+  MotionDirective,
+  MotionGroupComponent as MotionGroup,
+  MotionPlugin,
+} from '@vueuse/motion';