Update to support iOS 15 NativeLink™ feature (#41)

Full information in the Branch iOS SDK documentation here: https://help.branch.io/developers-hub/docs/ios-advanced-features#nativelink-deferred-deep-linking

Note: Requires Branch iOS SDK version 1.39.4 or higher, but I've implemented the method call in our kit wrapper to fail gracefully if using an older version of their SDK or if the new `checkPasteboardOnInstall` method is removed in the future for any reason.

Package.swift

@@ -16,7 +16,7 @@ let package = Package(
                .upToNextMajor(from: "8.2.0")),
       .package(name: "Branch",
                url: "https://github.com/BranchMetrics/ios-branch-sdk-spm",
-               .upToNextMajor(from: "1.39.1")),
+               .upToNextMajor(from: "1.39.4")),
     ],
     targets: [
         .target(

mParticle-BranchMetrics.podspec

@@ -16,5 +16,5 @@ Pod::Spec.new do |s|
     s.ios.deployment_target = "9.0"
     s.ios.source_files      = 'mParticle-BranchMetrics/*.{h,m,mm}'
     s.ios.dependency 'mParticle-Apple-SDK/mParticle', '~> 8.2'
-    s.ios.dependency 'Branch', '~> 1.39.1'
+    s.ios.dependency 'Branch', '~> 1.39.4'
 end

mParticle-BranchMetrics/MPKitBranchMetrics.m

@@ -160,6 +160,16 @@ - (void)start {
         [self.branchInstance registerPluginName:@"mParticle - iOS" version:MPKitBranchMetricsVersionNumber];
 
         if (self.enableAppleSearchAds) [self.branchInstance delayInitToCheckForSearchAds];
+
+        // iOS 15 Branch NativeLink™ support
+        // https://help.branch.io/developers-hub/docs/ios-advanced-features#nativelink-deferred-deep-linking
+        #pragma clang diagnostic push
+        #pragma clang diagnostic ignored "-Wundeclared-selector"
+        if ([Branch respondsToSelector:@selector(checkPasteboardOnInstall)]) {
+            [Branch performSelector:@selector(checkPasteboardOnInstall)];
+        }
+        #pragma clang diagnostic pop
+
         [self.branchInstance initSessionWithLaunchOptions:self.launchOptions
             isReferrable:YES
             andRegisterDeepLinkHandler:^(NSDictionary *params, NSError *error) {