Update RN min. version on Readme

Author: antonioolf

README.md

@@ -38,7 +38,7 @@ async checkSubscription() {
 1.  `npm install --save react-native-billing` or `yarn add react-native-billing`
 2.  `react-native link react-native-billing`
 
-With this, the `link`command will do most of the heavy lifting for native linking. **But**, you will still need add your Google Play license key to the `strings.xml` (step 5). If you are using a React Native version less than v18.0 you will also have to do step 4.3 (override `onActivityResult`).
+With this, the `link`command will do most of the heavy lifting for native linking. **But**, you will still need add your Google Play license key to the `strings.xml` (step 5). If you are using a React Native version less than v0.18 you will also have to do step 4.3 (override `onActivityResult`).
 
 ## Manual installation Android