Refactor to use js as extension

Author: wooorm

index.mjs renamed to index.js

@@ -23,11 +23,10 @@
     "Titus Wormer <tituswormer@gmail.com> (https://wooorm.com)"
   ],
   "type": "module",
-  "main": "./index.mjs",
-  "module": "./index.mjs",
+  "module": "./index.js",
   "types": "types",
   "files": [
-    "index.mjs",
+    "index.js",
     "types/index.d.ts"
   ],
   "dependencies": {
@@ -50,8 +49,8 @@
   },
   "scripts": {
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
-    "test-api": "node test.mjs",
-    "test-coverage": "c8 --check-coverage --branches 100 --functions 100 --lines 100 --statements 100 --reporter lcov node --experimental-modules test.mjs",
+    "test-api": "node test.js",
+    "test-coverage": "c8 --check-coverage --branches 100 --functions 100 --lines 100 --statements 100 --reporter lcov node --experimental-modules test.js",
     "test-types": "dtslint types",
     "test": "npm run format && npm run test-coverage && npm run test-types"
   },
@@ -66,9 +65,6 @@
   "xo": {
     "prettier": true,
     "esnext": false,
-    "extensions": [
-      "mjs"
-    ],
     "rules": {
       "complexity": "off",
       "eqeqeq": [

package.json

@@ -41,9 +41,11 @@ be imported instead of required.
 npm install xast-util-sitemap
 ```
 
+Note that this package is ESM only: it must be imported instead of required.
+
 ## Use
 
-Say we have the following module, `example.mjs`
+Say we have the following module, `example.js`
 
 ```js
 import {sitemap} from 'xast-util-sitemap'
@@ -66,7 +68,7 @@ var tree = sitemap([
 console.log(toXml(tree))
 ```
 
-Now, running `node example.mjs` yields (pretty printed):
+Now, running `node example.js` yields (pretty printed):
 
 ```xml
 <?xml version="1.0" encoding="utf-8"?>

readme.md

@@ -1,7 +1,7 @@
 'use strict'
 
 import test from 'tape'
-import {sitemap} from './index.mjs'
+import {sitemap} from './index.js'
 
 test('sitemap', function (t) {
   t.deepEqual(