feat(build): support commonjs modules (#4)

closes #3

Author: Shyam-Chen

package.json

@@ -2,8 +2,8 @@
   "name": "vue-router-prefetch",
   "version": "1.0.0",
   "description": "Prefetch the route components of router-link in viewport.",
-  "main": "dist/index.js",
-  "module": "dist/index.js",
+  "main": "dist/vue-router-prefetch.cjs.js",
+  "module": "dist/vue-router-prefetch.esm.js",
   "files": [
     "dist"
   ],

rollup.config.js

@@ -1,9 +1,13 @@
 export default {
   input: 'src/index.js',
-  output: {
-    format: 'es',
-    file: 'dist/index.js'
-  },
+  output: [
+    {
+      file: 'dist/vue-router-prefetch.cjs.js',
+      format: 'cjs',
+      exports: 'named'
+    },
+    { file: 'dist/vue-router-prefetch.esm.js', format: 'es' }
+  ],
   plugins: [
     require('rollup-plugin-node-resolve')(),
     require('rollup-plugin-buble')({

src/index.js

@@ -1,9 +1,7 @@
 import prefetch from './prefetch'
 import { canPrefetch, supportIntersectionObserver } from './utils'
 
-export { prefetch }
-
-export default (Vue, { componentName = 'RouterLink' } = {}) => {
+function installRouterPrefetch(Vue, { componentName = 'RouterLink' } = {}) {
   const observer =
     supportIntersectionObserver &&
     new window.IntersectionObserver(entries => {
@@ -83,3 +81,11 @@ export default (Vue, { componentName = 'RouterLink' } = {}) => {
 
   Vue.component(Link.name, Link)
 }
+
+export {
+  prefetch,
+  // Export as `install` to make `Vue.use(require('vue-router-prefetch'))` work
+  installRouterPrefetch as install
+}
+
+export default installRouterPrefetch