Merge pull request #5748 from Countly/push-readme

[push] added README.md

Author: ArtursKadikis

plugins/push/README.md

@@ -0,0 +1,12 @@
+# Countly Push Plugin
+
+These URLs need to be accessible by the Countly instance:
+
+- for Android:
+	- fcm.googleapis.com
+	- accounts.google.com
+- for IOS:
+	- api.development.push.apple.com
+	- api.push.apple.com
+- for Huawei
+	- push-api.cloud.huawei.com