Revert "Merge pull request frontity#834 from frontity/with-preact-as-…

…commonjs"

This reverts commit d1d16d4, reversing
changes made to c5b4f80.

packages/with-preact/frontity.config.js

@@ -3,7 +3,7 @@
  *
  * @param param - The passed params.
  */
-module.exports.webpack = ({ config }) => {
+export const webpack = ({ config }) => {
   config.resolve.alias["react"] = "preact/compat";
   config.resolve.alias["react-dom"] = "preact/compat";
 };