config: Replace webpack configs with FEC config

This migrates from previously used webpack configs to one fec.config.js.

This will allow us to bump `frontend-components-config` dependency to version 6.x and stay supported in the future.

fec.config.js

@@ -0,0 +1,93 @@
+/* eslint-disable @typescript-eslint/no-var-requires */
+const path = require('path');
+
+const CopyPlugin = require('copy-webpack-plugin');
+const webpack = require('webpack');
+
+const plugins = [];
+
+if (process.env.MSW) {
+  // Copy mockServiceWorker.js to ./dist/ so it is served with the bundle
+  plugins.push(
+    new CopyPlugin({
+      patterns: [
+        { from: 'src/mockServiceWorker.js', to: 'mockServiceWorker.js' },
+      ],
+    })
+  );
+
+  /*
+  We would like the client to be able to determine whether or not to start
+  the service worker at run time based on the value of process.env.MSW. We can
+  add that variable to process.env via the DefinesPlugin plugin, but
+  DefinePlugin has already been added by config() to the default webpackConfig.
+
+  Therefore, we find it in the `plugins` array based on its type, then update
+  it to add our new process.env.MSW variable.
+  */
+  const definePluginIndex = plugins.findIndex(
+    (plugin) => plugin instanceof webpack.DefinePlugin
+  );
+  const definePlugin = plugins[definePluginIndex];
+
+  const newDefinePlugin = new webpack.DefinePlugin({
+    ...definePlugin.definitions,
+    'process.env.MSW': true,
+  });
+
+  plugins[definePluginIndex] = newDefinePlugin;
+}
+
+module.exports = {
+  sassPrefix: '.imageBuilder',
+  debug: true,
+  useFileHash: false,
+  /*
+  mockServiceWorker.js will be served from /beta/apps/image-builder, which
+  will become its default scope. Setting the Service-Worker-Allowed header to
+  '/' allows the worker's scope to be expanded to the root route '/'.
+
+  The default webpackConfig for stage does not contain any headers.
+
+  Caution: The default webpackConfig for prod *does* contain headers, so this
+  code will need to be modified if using MSW in prod-beta or prod-stable so that
+  those headers are not overwritten.
+  */
+  devServer: process.env.MSW && {
+    headers: { 'Service-Worker-Allowed': '/' },
+  },
+  appUrl: '/insights/image-builder',
+  useProxy: true,
+  useAgent: true,
+  bounceProd: false,
+  proxyVerbose: true,
+  routes: {
+    ...(process.env.CONFIG_PORT && {
+      [`${process.env.BETA ? '/beta' : ''}/config`]: {
+        host: `http://localhost:${process.env.CONFIG_PORT}`,
+      },
+    }),
+    ...(process.env.LOCAL_API && {
+      ...(process.env.LOCAL_API.split(',') || []).reduce((acc, curr) => {
+        const [appName, appConfig] = (curr || '').split(':');
+        const [appPort = 8003, protocol = 'http', host = 'localhost'] =
+          appConfig.split('~');
+        return {
+          ...acc,
+          [`/apps/${appName}`]: { host: `${protocol}://${host}:${appPort}` },
+          [`/beta/apps/${appName}`]: {
+            host: `${protocol}://${host}:${appPort}`,
+          },
+        };
+      }, {}),
+    }),
+  },
+  plugins: plugins,
+  moduleFederation: {
+    exposes: {
+      './RootApp': path.resolve(__dirname, './src/AppEntry.tsx'),
+    },
+    shared: [{ 'react-router-dom': { singleton: true, version: '*' } }],
+    exclude: ['react-router-dom'],
+  },
+};