Added an OpenAPI validation target and license headers.

README.md

@@ -12,7 +12,7 @@ Add `ASConnectService` as a dependency in your `Package.swift` file:
 
 ```swift
 dependencies: [
-    .package(url: "https://github.com/rock-n-code/asconnect-service.git", from: "1.0.0")
+    .package(url: "https://github.com/rock-n-code/asconnect-service.git", from: "2.0.0")
 ]
 ```
 
@@ -142,6 +142,9 @@ make oas-download
 
 # Regenerate the code only
 make oas-generate
+
+# Validate the specification only
+make oas-validate
 ```
 
 ## Dependencies