Update macOS platform version to v13

Author: MaxDesiatov

Package.swift

@@ -20,7 +20,7 @@ let testingLinkerFlags: [LinkerSetting] = [
 let package = Package(
     name: "JavaScriptKit",
     platforms: [
-        .macOS(.v10_15),
+        .macOS(.v13),
         .iOS(.v13),
         .tvOS(.v13),
         .watchOS(.v6),