Added missing BranchSDK Header file

Author: Harsha Bonthu

plugin.xml

@@ -102,6 +102,7 @@ SOFTWARE.
                 </dict>
             </array>
         </config-file>
+        <header-file src="src/ios/BranchSDK.h" />
         <source-file src="src/ios/BranchSDK.m" />
         <source-file src="src/ios/AppDelegate+BranchSdk.m" />
         <framework custom="true" src="src/ios/dependencies/Branch.framework" />