Add methods for using mock data

[cooperka]

Motivation

Neither Android nor iOS has good support for mocking activity recognition (see this answer and this library to get an idea). It's very difficult to test a production app without some way of mocking these events.

Changes

• Added methods for startMocked and stopMocked (both iOS and Android)
• Exported some basic constants to use as mock activity types, based on platform
• Made JS method exports consistent across Android and iOS (previously Android exported the native module directly with all of its raw methods; now it's a separate object like iOS)

⚠️ Note: This PR is currently based on https://github.com/Aminoid/react-native-activity-recognition/pull/4, so the diff is inaccurate. See here for the real diff. I can rebase after #4 is merged.

Example

const mockActivity = Platform.OS === 'ios'
  ? ActivityRecognition.IOS_AUTOMOTIVE
  : ActivityRecognition.ANDROID_IN_VEHICLE;

ActivityRecognition.startMocked(1000, mockActivity);
ActivityRecognition.stopMocked();

[Aminoid]

Thanks for the request @cooperka. Merged and is available in v3.2.0