Add PromiseKit dependency

- Added PromiseKit dependency

Carthage/Checkouts/PromiseKit/Extensions/MapKit/Sources/MKMapSnapshotter+AnyPromise.h

@@ -0,0 +1,23 @@
+#import <MapKit/MKMapSnapshotter.h>
+#import <PromiseKit/AnyPromise.h>
+
+/**
+ To import the `MKMapSnapshotter` category:
+
+    use_frameworks!
+    pod "PromiseKit/MapKit"
+
+ And then in your sources:
+
+    @import PromiseKit;
+*/
+@interface MKMapSnapshotter (PromiseKit)
+
+/**
+ Starts generating the snapshot using the options set in this object.
+
+ @return A promise that fulfills with the generated `MKMapSnapshot` object.
+*/
+- (AnyPromise *)start NS_REFINED_FOR_SWIFT;
+
+@end