Add example in the example MergeFile and add a draft of the README

Author: David McRae

PodMergeExample/MergeFile

@@ -11,12 +11,13 @@ group 'UI'
 end
 
 group 'MergedSwiftPods' do
-  pod 'SnapKit'
-  pod 'SwiftyJSON'
+	pod 'SnapKit'
+	pod 'SwiftyJSON'
 end
 
 group 'AlamofireGroup' do
 	swift_version! '5.0'
+	platform :ios, '11.0'
 	has_dependencies!
 
 	pod 'Alamofire'

README.md

@@ -199,6 +199,22 @@ end
 
 This is especially handy if some of the pods in your group do not have a Swift Version defined in their `podspec`.
 
+#### platform
+
+If you have multiple platforms in your base Podfile, you can specify the `platform` for each group in your MergeFile
+
+```ruby
+group 'SwiftPodsGroup'
+	platform :ios, '11.0'
+
+	pod 'SwiftPodA'
+	pod 'SwiftPodB'
+	pod 'SwiftPodC'
+end
+```
+
+This is helpful when you have a Podfile with Pods for iOS, WatchOS, etc...
+
 ## Version Control (like git)
 
 You should definitely commit the `MergeFile`  into your repository, since this is just like your Podfile, and is required for the plugin to work.