Throw an error if the native module is null with steps to help fix the issue

[matt-oakes]

Overview

Shows a helpful error message if linking has not been done correctly and the native module is null. It gives the steps that are most likely to fix the issue.

Before:

After:

This will help to diagnose linking issues like #30.

Test Plan

Delete RNCNetInfo.a from the "Linked Frameworks and Libraries" section and see the new error message.

[react-native-community-bot]

🎉 This PR is included in version 1.4.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[viktorlarsson]

Had some issues with the CI environment failing with the following issue:

@react-native-community/netinfo: NativeModule.RNCNetInfo is null. To fix this issue try these steps:

Missed that you need to mock netinfo (if someone elses sees this)

jest.mock('@react-native-community/netinfo', () => ({
  getConnectionInfo: jest.fn()
}));