Add swift-syntax version comment to Package manifest (#27)

Author: graycampbell

Package.swift

@@ -25,7 +25,7 @@ let package = Package(
     dependencies: [
         .package(
             url: "https://github.com/apple/swift-syntax.git",
-            exact: "600.0.0"
+            exact: "600.0.0" // Must match SwiftSyntaxSugar's swift-syntax version
         ),
         .package(
             url: "https://github.com/fetch-rewards/SwiftSyntaxSugar.git",