Detect macOS Catalyst (#8)

* Detect macOS Catalyst

It is currently reported as iOS, which in some technical senses is
somewhat true - but does not fully capture the semantics of where
the app is actually run (which is on a Mac running macOS).

* Increase minimum Swift version to 5.6

Needed to support "targetEnvironment" to detect macOS Catalyst.

* Report OS name as "macOS"

Aptabase.podspec

@@ -10,6 +10,6 @@ Pod::Spec.new do |s|
     s.osx.deployment_target     = "10.15"
     s.watchos.deployment_target = "6.0"
     s.tvos.deployment_target    = "13.0"
-    s.swift_version             = '5.5'
+    s.swift_version             = '5.6'
     s.source_files              = 'Sources/Aptabase/**/*'
   end

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version: 5.5
+// swift-tools-version: 5.6
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription

Sources/Aptabase/EnvironmentInfo.swift

@@ -39,7 +39,7 @@ struct EnvironmentInfo {
     }
     
     private static var osName: String {
-        #if os(macOS)
+        #if os(macOS) || targetEnvironment(macCatalyst)
         "macOS"
 #elseif os(iOS)
         if UIDevice.current.userInterfaceIdiom == .pad {
@@ -56,7 +56,7 @@ struct EnvironmentInfo {
     }
     
     private static var osVersion: String {
-        #if os(macOS)
+        #if os(macOS) || targetEnvironment(macCatalyst)
         let os = ProcessInfo.processInfo.operatingSystemVersion
         return "\(os.majorVersion).\(os.minorVersion).\(os.patchVersion)"
         #elseif os(iOS)