Update Firebase podspec for watchOS (#4808)

Firebase.podspec

@@ -48,6 +48,11 @@ Simplify your iOS development, grow your user base, and monetize more effectivel
         'HEADER_SEARCH_PATHS' => "$(inherited) ${PODS_ROOT}/Firebase/CoreOnly/Sources"
       }
     end
+    # Standard platforms PLUS watchOS.
+    ss.ios.deployment_target = '8.0'
+    ss.osx.deployment_target = '10.11'
+    ss.tvos.deployment_target = '10.0'
+    ss.watchos.deployment_target = '6.0'
   end
 
   s.subspec 'Analytics' do |ss|
@@ -109,6 +114,11 @@ Simplify your iOS development, grow your user base, and monetize more effectivel
   s.subspec 'Messaging' do |ss|
     ss.dependency 'Firebase/CoreOnly'
     ss.dependency 'FirebaseMessaging', '~> 4.2.0'
+    # Standard platforms PLUS watchOS.
+    ss.ios.deployment_target = '8.0'
+    ss.osx.deployment_target = '10.11'
+    ss.tvos.deployment_target = '10.0'
+    ss.watchos.deployment_target = '6.0'
   end
 
   s.subspec 'Performance' do |ss|

Firebase/Messaging/CHANGELOG.md

@@ -1,3 +1,6 @@
+# 2020-02 -- v 4.2.1
+- [added] Firebase Pod support for watchOS: `pod 'Firebase/Messaging'` in addition to `pod 'FirebaseMessaging'`. (#4807)
+
 # 2020-01 -- v 4.2.0
 - [added] Added watchOS support for Firebase Messaging. This enables FCM push notification function on watch only app or independent watch app. (#4016)
 - [added] Added a new transitive dependency on the [Firebase Installations SDK](../../FirebaseInstallations/CHANGELOG.md). The Firebase Installations SDK introduces the [Firebase Installations API](https://console.cloud.google.com/apis/library/firebaseinstallations.googleapis.com). Developers that use API-restrictions for their API-Keys may experience blocked requests (https://stackoverflow.com/questions/58495985/). A solution is available [here](../../FirebaseInstallations/API_KEY_RESTRICTIONS.md).