fix(build): fix production build library export

Author: chrisboustead

package.json

@@ -14,7 +14,7 @@
   "version": "1.2.2",
   "homepage": "https://github.com/chrisboustead/netlify-cms-widget-async-select",
   "license": "MIT",
-  "main": "dist/main.js",
+  "main": "dist/index.js",
   "devDependencies": {
     "@babel/core": "^7.0.0",
     "@babel/plugin-proposal-class-properties": "^7.0.0",

webpack.config.js

@@ -50,8 +50,7 @@ const developmentConfig = {
 const productionConfig = {
   mode: 'production',
   entry: {
-      AsyncSelectControl: ['./src/Control.js'],
-      AsyncSelectPreview: ['./src/Preview.js']
+      index: ['./src/index.js']
   },
   module: {
     rules: [