feat: adding types definition and ESM usage to README

Author: chrisprobably

README.md

@@ -14,15 +14,29 @@ or:
 
 `yarn add accept-language-middleware`
 
-Usage:
+Usage (ESM):
 
+```js
+import express from "express";
+import acceptLanguageMiddleware from "accept-language-middleware";
+
+const app = express();
+app.use(acceptLanguageMiddleware());
+app.get("/", (req, res, next) => {
+  console.log(req.language); // 'en'
+  console.log(req.locale); // 'en-US'
+});
 ```
-var express = require('express');
+
+Usage (CJS):
+
+```js
+var express = require("express");
 var app = express();
 var acceptLanguageMiddleware = require("accept-language-middleware");
 
 app.use(acceptLanguageMiddleware());
-app.get('/', function(req, res, next) {
+app.get("/", function (req, res, next) {
   console.log(req.language); // 'en'
   console.log(req.locale); // 'en-US'
 });
@@ -34,15 +48,15 @@ app.get('/', function(req, res, next) {
 
 Specify a default language to fallback on if none is passed:
 
-```
+```js
 app.use(acceptLanguageMiddleware({ default: "es" }));
 ```
 
 ### supported (by default all languages are supported)
 
 Specify a set of supported languages, if the incoming Accept-Language header does not contain a language in the supported list, then the default language will be used.
 
-```
+```js
 app.use(acceptLanguageMiddleware({ supported: ["en", "es", "zh"] }));
 ```
 

index.d.ts

@@ -0,0 +1,26 @@
+import { RequestHandler } from "express";
+
+declare namespace AcceptLanguageMiddleware {
+  interface Options {
+    default?: string;
+    supported?: string[];
+  }
+
+  interface AugmentedRequest {
+    language?: string;
+    locale?: string;
+  }
+}
+
+declare module "express-serve-static-core" {
+  interface Request {
+    language?: string;
+    locale?: string;
+  }
+}
+
+declare function acceptLanguageMiddleware(
+  options?: AcceptLanguageMiddleware.Options
+): RequestHandler;
+
+export = acceptLanguageMiddleware;

package.json

@@ -14,10 +14,12 @@
   "scripts": {
     "test": "tap test/*.js"
   },
+  "types": "index.d.ts",
   "files": [
     "LICENSE",
     "README.md",
-    "index.js"
+    "index.js",
+    "index.d.ts"
   ],
   "engines": {
     "node": ">=18.0.0"