add comments noting when nodes start and end

src/index.ts

@@ -68,6 +68,7 @@ function resolveNode(
 ) {
   // deno-lint-ignore prefer-const
   let instructions: string[] = [];
+  instructions.push(`/* start ${node.type} */`);
   switch (node.type) {
     case "VariableDeclaration": {
       VariableDeclaration(
@@ -122,6 +123,7 @@ function resolveNode(
     default:
       throw new Error(`Unimplemented node ${node.type}`);
   }
+  instructions.push(`/* end ${node.type} */`);
   return instructions;
 }