fix: cjs import (#730)

BREAKING CHANGE: fix compatibility with CommonJS

Author: evilebottnawi

package.json

@@ -7,7 +7,7 @@
   "author": "Tobias Koppers @sokra",
   "homepage": "https://github.com/webpack/webpack-dev-middleware",
   "bugs": "https://github.com/webpack/webpack-dev-middleware/issues",
-  "main": "dist/index.js",
+  "main": "dist/cjs.js",
   "funding": {
     "type": "opencollective",
     "url": "https://opencollective.com/webpack"

src/cjs.js

@@ -0,0 +1,3 @@
+const middleware = require('./index');
+
+module.exports = middleware.default;

test/cjs.test.js

@@ -0,0 +1,8 @@
+import src from '../src';
+import cjs from '../src/cjs';
+
+describe('cjs', () => {
+  it('should work', () => {
+    expect(cjs).toEqual(src);
+  });
+});