Update README.md

README.md

@@ -1,8 +1,19 @@
 [![build status](https://github.com/jg210/expo-experiments/actions/workflows/checks.yml/badge.svg)](https://github.com/jg210/expo-experiments/actions/workflows/checks.yml)
 
+A [react native](https://reactnative.dev/)/[Expo](https://expo.dev/) app for testing out new technologies. It shows data from the [spring-experiments](https://github.com/jg210/spring-experiments) API.
+
 Expo is setting up an adb reverse tunnel, but doesn't use it unless tell it to with this env. var.:
 
+## Development Build Instructions
+
+Install nodenv and node-build (or use any other way to put correct version of node on PATH):
+
+* https://github.com/nodenv/nodenv#installation
+* https://github.com/nodenv/node-build#installation
+
+To run the app (on android), (setting environment variable to avoid problem from expo not using the adb reverse tunnel it sets up):
+
 ```
 . environment
 REACT_NATIVE_PACKAGER_HOSTNAME=localhost npm run android --localhost
-```
+```