Add Jest Mock for RNCallKeep

Problem

• I need to be able to use RN-callkeep without a native device being required.

Invariant Violation: Native module cannot be null.

  at invariant (node_modules/invariant/invariant.js:40:15)
  at new NativeEventEmitter (node_modules/react-native/Libraries/EventEmitter/NativeEventEmitter.js:36:7)
  at Object.<anonymous> (node_modules/react-native-callkeep/actions.js:4:22)
  at Object.<anonymous> (node_modules/react-native-callkeep/index.js:3:1)\

Proposal

I would like to add a jest mock similar to how these libraries have implemented jest/ folders for easy import

PATH /jest/react-native-call-keep-mock.js

• react-native-netinfo
• react-native-async-storage
• react-native-device-info

Approach

• All external methods on RNCallKeep complete
• No regression in tests
• Update readme to notify about how to test

Notes

Beginne damit, die angeforderte /jest/react-native-call-keep-mock.js mit den verlinkten Jest-Mock-Implementierungen zu vergleichen. Untersuche die externen Methoden von RNCallKeep und die vorhandenen Tests und aktualisiere anschließend die README mit Nutzungsanweisungen. Als erledigt gilt die Aufgabe, wenn der Mock alle externen Methoden abdeckt und die Testsuite keine Regressionen aufweist.