Update README.md to make expo-package path clear (#3123)

The readme was a bit confusing - it should mention that expo-package is under the package directory.  I looked for it at the root and didn't see it.

Author: tleyden

examples/ExpoMessaging/README.md

@@ -26,7 +26,7 @@ yarn install
 cd package && yarn install
 ```
 
-3. Move to the `expo-package` directory and install the dependencies:
+3. Move to the `package/expo-package` directory and install the dependencies:
 
 ```bash
 cd expo-package && yarn install
@@ -68,4 +68,4 @@ hermesEnabled=true
 # disables the check for multiple instances for gesture handler
 # this is needed for react-native-gesture-handler to be both a devDep of core and be a dep on the expo sample app
 disableMultipleInstancesCheck=true
-```
+```