Add an issue template

ISSUE_TEMPLATE.md

@@ -3,4 +3,4 @@ Please consider submitting the following information:
 * Library setup method: file, Carthage, CocoaPods or Swift Package Manager.
 * Version of the library. Example: 8.0.
 * Xcode version. Example: 8.3.3.
-* iOS version. Example: 10.3.2.
+* OS version. Example: iOS 10.3.2.