feat: add getCalls method for ios only

[Jerome91410]

getCalls

This feature is available only on IOS.

Returns a Promise. The result will be an array with all current calls and their states.

RNCallKeep.getCalls();

response:
[{
  callUUID: "E26B14F7-2CDF-48D0-9925-532199AE7C48"
  hasConnected: true
  hasEnded: false
  onHold: false
  outgoing: false
}]