feat: Add DO NOT EDIT comment to files

Author: kyleconroy

src/app.ts

@@ -278,7 +278,7 @@ function printNode(nodes: Node[]): string {
     ScriptKind.TS
   );
   const printer = createPrinter({ newLine: NewLineKind.LineFeed });
-  let output = "";
+  let output = "// Code generated by sqlc. DO NOT EDIT.\n\n";
   for (let node of nodes) {
     output += printer.printNode(EmitHint.Unspecified, node, resultFile);
     output += "\n\n";