Remove Package.resolved files and uncomment .gitignore entry

Author: AlexNachbaur

.gitignore

@@ -44,7 +44,7 @@ playground.xcworkspace
 # Add this line if you want to avoid checking in source code from Swift Package Manager dependencies.
 # Packages/
 # Package.pins
-# Package.resolved
+Package.resolved
 .build/
 .swiftpm/