(chore) dual package (#3188)

Avoid dual package hazard by making our ES6 modules simply require our CJS modules.  (for HLJS core, so that someone pulling in the library by both ES and CJS will not have two different instances)

Per https://nodejs.org/api/packages.html#packages_writing_dual_packages_while_avoiding_or_minimizing_hazards

tools/build_node.js

@@ -8,25 +8,13 @@ const { filter } = require("./lib/dependencies");
 const { rollupWrite } = require("./lib/bundling.js");
 const log = (...args) => console.log(...args);
 
-const safeImportName = (s) => {
-  s = s.replace(/-/g, "_");
-  if (/^\d/.test(s)) s = `L_${s}`;
-  return s;
-};
-
-async function buildESMIndex(name, languages) {
-  const header = `import hljs from './core.js';`;
-  const footer = "export default hljs;";
-
-
-  const registration = languages.map((lang) => {
-    const importName = safeImportName(lang.name);
-    return `import ${importName} from './languages/${lang.name}.js';\n` +
-      `hljs.registerLanguage('${lang.name}', ${importName});`;
-  });
-
-  const index = `${header}\n\n${registration.join("\n")}\n\n${footer}`;
-  await fs.writeFile(`${process.env.BUILD_DIR}/es/${name}.js`, index);
+// https://nodejs.org/api/packages.html#packages_writing_dual_packages_while_avoiding_or_minimizing_hazards
+async function buildESMStub(name) {
+  const code =
+    `// https://nodejs.org/api/packages.html#packages_writing_dual_packages_while_avoiding_or_minimizing_hazards\n` +
+    `import hljs from '../lib/${name}.js';\n` +
+    `export default hljs;\n`;
+  await fs.writeFile(`${process.env.BUILD_DIR}/es/${name}.js`, code);
 }
 
 async function buildCJSIndex(name, languages) {
@@ -97,11 +85,7 @@ async function buildNodeHighlightJS(options) {
   const output = { ...config.rollup.node.output, file: `${process.env.BUILD_DIR}/lib/core.js` };
   await rollupWrite(input, output);
   if (options.esm) {
-    await rollupWrite(input, {
-      ...output,
-      format: "es",
-      file: `${process.env.BUILD_DIR}/es/core.js`
-    });
+    buildESMStub("core");
   }
 }
 
@@ -191,8 +175,8 @@ async function buildNode(options) {
 
   if (options.esm) {
     await fs.writeFile(`${process.env.BUILD_DIR}/es/package.json`, `{ "type": "module" }`);
-    await buildESMIndex("index", languages);
-    await buildESMIndex("common", common);
+    await buildESMStub("index");
+    await buildESMStub("common");
     await buildESMUtils();
   }
   await buildCJSIndex("index", languages);