refactor: convert source to ESM with dual ESM/CJS build

- Set "type": "module" in package.json
- Add `exports` field with import/require conditions; build to dist/esm and dist/cjs
- Source uses `import schema from "./options.json" with { type: "json" }`
  and `.js`-suffixed relative imports
- Load less via `await import(normalizeImportSpecifier(pkg))`; the babel
  CommonJS transform now skips dynamic-import lowering so the CJS dist
  keeps native `import()`
- Drop src/cjs.js and test/cjs.test.js (obsolete with dual build)
- Point test getCompiler at dist/cjs/index.js
- Allow ES2025 syntax in eslint
- Convert lint-staged.config.js to ESM
- Remove commitlint entirely: config file, npm script, husky commit-msg
  hook, devDependencies, .cspell word, and CI step

Author: claude

.changeset/convert-to-esm.md

@@ -0,0 +1,5 @@
+---
+"less-loader": major
+---
+
+The package now ships native ESM as well as CommonJS. `"type": "module"` is set, and an `exports` map exposes `dist/esm/index.js` to `import` and `dist/cjs/index.js` to `require`. Less is loaded via dynamic `import()` instead of `require()`.

.cspell.json

@@ -10,8 +10,7 @@
     "iscolor",
     "klona",
     "FOUC",
-    "sourcemaps",
-    "commitlint"
+    "sourcemaps"
   ],
 
   "ignorePaths": [

.github/workflows/nodejs.yml

@@ -52,10 +52,6 @@ jobs:
       - name: Security audit
         run: npm run security
 
-      - name: Validate PR commits with commitlint
-        if: github.event_name == 'pull_request'
-        run: npx commitlint --from ${{ github.event.pull_request.head.sha }}~${{ github.event.pull_request.commits }} --to ${{ github.event.pull_request.head.sha }} --verbose
-
   test:
     name: Test - ${{ matrix.os }} - Node v${{ matrix.node-version }}, Webpack ${{ matrix.webpack-version }}
 

.husky/commit-msg

@@ -1,8 +1,10 @@
 const MIN_BABEL_VERSION = 7;
 
-module.exports = (api) => {
+export default (api) => {
   api.assertVersion(MIN_BABEL_VERSION);
-  api.cache(true);
+
+  const env = api.env();
+  const isEsm = env === "esm";
 
   return {
     presets: [
@@ -12,6 +14,8 @@ module.exports = (api) => {
           targets: {
             node: "22.11.0",
           },
+          modules: isEsm ? false : "commonjs",
+          exclude: ["transform-dynamic-import"],
         },
       ],
     ],

babel.config.js

@@ -9,6 +9,9 @@ const __dirname = path.dirname(fileURLToPath(import.meta.url));
 export default defineConfig([
   {
     extends: [configs["recommended-dirty"]],
+    languageOptions: {
+      ecmaVersion: 2025,
+    },
   },
   {
     files: ["test/**/*.{js,cjs,mjs}"],

commitlint.config.js

@@ -1,4 +1,4 @@
-module.exports = {
+export default {
   "*": [
     "prettier --cache --write --ignore-unknown",
     "cspell --cache --no-must-find-files",