Add tutorial steps to README

Author: lorensr

README.md

@@ -7,6 +7,13 @@ This example app is built, tutorial-style, in the React Native chapter of [The G
   - [src/HomeScreen.js](https://github.com/GraphQLGuide/guide-react-native/blob/master/src/HomeScreen.js)
   - [src/ChapterScreen.js](https://github.com/GraphQLGuide/guide-react-native/blob/master/src/ChapterScreen.js)
 
+Tutorial steps:
+
+- [Starting branch: 0](https://github.com/GraphQLGuide/guide-react-native/tree/0) app skeleton
+- [Step 1: 0...1](https://github.com/GraphQLGuide/guide-react-native/compare/0...1) adding Apollo Client and first query
+- [Step 2: 1...2](https://github.com/GraphQLGuide/guide-react-native/compare/1...2) adding second screen and query
+- [Step 3: 2...3](https://github.com/GraphQLGuide/guide-react-native/compare/2...3) persisting the cache
+
 ### Running the app
 
 ```sh