Apple Calendar map support

[focux]

Close #157

This PR adds support for Apple's Calendar Map. I added a new property to the event model called appleLocation. This is the interface of that new property:

    interface AppleLocationData {
      title: string;
      address: string;
      radius: number;
      geo: GeoData;
    }

    interface GeoData {
      lat: number;
      lon: number;
    }

I decided to doesn't allow the use of location and appleLocation in the same event, because, if they don't have the same title and address, the map won't work. So, if you use the appleLocation property, it'll create under the hood the location and the X-APPLE-STRUCTURED-LOCATION, this way, it will always match.

e.g. This object

{
  ...
  appleLocation: {
    title: 'My Title',
    address: 'My Address',
    radius: 40,
    geo: {
      lat: '52.063921',
      lon: '5.128511',
    }
  ...
}

Will output this:

...
LOCATION:My Title\nMy Address
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=My Address;X-APPLE-
 RADIUS=40;X-TITLE=My Title:geo:52.063921,5.128511
...

This PR also contain the type definitions for this implementation, although I missed the test and the docs.

[sebbo2002]

• Unit Tests
• Documentation

[sebbo2002]

Just released ical-generator v1.10.0 with this feature. Thanks again.