Support dual bundle ESM/CJS

.eslintignore

@@ -0,0 +1 @@
+lib

.eslintrc.yml

@@ -3,6 +3,19 @@ env:
   es6: true
 extends:
   - 'eslint:recommended'
+  - 'plugin:node/recommended'
+  - 'plugin:import/recommended'
   - 'prettier'
 parserOptions:
   ecmaVersion: 2020
+rules:
+  no-console: error
+  prefer-const: error
+  no-var: error
+  no-use-before-define: error
+  no-await-in-loop: error
+  node/exports-style: [0, error]
+  import/first: error
+  import/no-anonymous-default-export: error
+  import/no-unassigned-import: error
+  import/no-internal-modules: error

.gitignore

@@ -5,4 +5,5 @@ npm-debug.log*
 .nyc_output
 coverage.info
 test/fixtures/*/build
-node_modules
+node_modules
+lib

README.md

@@ -27,7 +27,7 @@ yarn add @metalsmith/drafts
 Pass the plugin with any options to `Metalsmith.use`.
 
 ```js
-const drafts = require('@metalsmith/drafts')
+import drafts from '@metalsmith/drafts'
 
 metalsmith.use(drafts()) // same as { include: false }
 metalsmith.use(drafts(true)) // same as { include: true }
@@ -56,7 +56,7 @@ metalsmith.use(drafts(inDevelopment))
 You can instruct `@metalsmith/drafts` to mark files as `draft` by default if they don't have a `draft` property in their front-matter:
 
 ```js
-const drafts = require('@metalsmith/drafts')
+import drafts from '@metalsmith/drafts'
 
 metalsmith.use(
   drafts({