fix: use webpack for dev-server to keep consistent css-module classnames

There's an inconsistency between webpack and next turbo's `localIdentName`

This also improves the hot-loading

fixes #440

postcss.config.js

@@ -1,23 +1,17 @@
 module.exports = {
-  plugins:
-    process.env.NODE_ENV === "production"
-      ? [
-          "postcss-nested",
-          [
-            "postcss-preset-env",
-            {
-              autoprefixer: {
-                flexbox: "no-2009",
-              },
-              stage: 3,
-              features: {
-                "custom-properties": false,
-              },
-            },
-          ],
-        ]
-      : [
-          // No transformations in development
-          // because it won't affect turbo
-        ],
+  plugins: [
+    "postcss-nested",
+    [
+      "postcss-preset-env",
+      {
+        autoprefixer: {
+          flexbox: "no-2009",
+        },
+        stage: 3,
+        features: {
+          "custom-properties": false,
+        },
+      },
+    ],
+  ],
 };