Refactor into monorepo for v6 (#1837)

> You can [learn more about this here](https://blog.invertase.io/react-native-firebase-2019-7e334ca9bcc6).

packages/analytics/ios/RNFBAnalytics.podspec

@@ -0,0 +1,20 @@
+require 'json'
+package = JSON.parse(File.read('../package.json'))
+
+Pod::Spec.new do |s|
+  s.name                = "RNFBAnalytics"
+  s.version             = package["version"]
+  s.description         = package["description"]
+  s.summary             = <<-DESC
+                            A well tested feature rich Firebase implementation for React Native, supporting iOS & Android.
+                          DESC
+  s.homepage            = "http://invertase.io/oss/react-native-firebase"
+  s.license             = package['license']
+  s.authors             = "Invertase Limited"
+  s.source              = { :git => "https://github.com/invertase/react-native-firebase.git", :tag => "v#{s.version}" }
+  s.social_media_url    = 'http://twitter.com/invertaseio'
+  s.platform            = :ios, "10.0"
+  s.source_files        = 'RNFBAnalytics/**/*.{h,m}'
+  s.dependency          'React'
+  s.dependency          'Firebase/Core', '~> 5.15.0'
+end