feature: enable multiple file types per entry

It is possible to provide different types of files when using an
array of values for entry to achieve separate bundles for CSS
and JavaScript (and other) files in applications that are not using
import for styles in JavaScript (pre Single Page Applications or
different reasons).

For additional info: https://webpack.js.org/guides/entry-advanced/

This is particularly useful if you are migrating from a per page
css/js organization as was common with rails <= 6

package/environments/base.js

@@ -65,7 +65,11 @@ const getEntryObject = () => {
   paths.forEach((path) => {
     const namespace = relative(join(rootPath), dirname(path))
     const name = join(namespace, basename(path, extname(path)))
-    result.set(name, resolve(path))
+
+    // Allows for multiple filetypes per entry (https://webpack.js.org/guides/entry-advanced/)
+    let resultList = result.get(name) || []
+    resultList.push(resolve(path))
+    result.set(name, resultList)
   })
   return result
 }