fix: allow using absent file path as an output

This commit adds support for specifying an absent output file path and makes sure we generate it if it doesn't exist yet.

Sources/SwiftGraphQLCLI/main.swift

@@ -59,7 +59,7 @@ struct SwiftGraphQLCLI: ParsableCommand {
 
         // Write to target file or stdout.
         if let outputPath = output {
-            try Folder.current.file(at: outputPath).write(code)
+            try Folder.current.createFile(at: outputPath).write(code)
         } else {
             FileHandle.standardOutput.write(code.data(using: .utf8)!)
         }