add example to earn pub points

package/example/README.md

@@ -0,0 +1,12 @@
+# Examples
+
+Run the [example application](https://github.com/fujidaiti/exprollable_page_view/tree/master/example) and explore the all features of this package.
+
+```shell
+git clone [email protected]:fujidaiti/exprollable_page_view.git
+cd example
+flutter pub get
+flutter run
+```
+
+There is another example, which demonstrates how `ExprollablePageView` is able to work with Google Maps. See [maps_example/README](https://github.com/fujidaiti/exprollable_page_view/blob/master/maps_example/README.md) for more details.