build: add rollup config to handle css modules

package.json

@@ -106,6 +106,7 @@
     "react": "^17.0.1",
     "react-dom": "^17.0.1",
     "react-is": "^17.0.1",
+    "rollup-plugin-postcss": "^4.0.2",
     "size-limit": "^11.0.1",
     "storybook": "^7.6.7",
     "tsdx": "^0.14.1",

tsdx.config.js

@@ -0,0 +1,14 @@
+const postcss = require('rollup-plugin-postcss');
+
+module.exports = {
+  rollup(config, options) {
+    config.plugins.push(
+      postcss({
+        modules: true,
+        // only write out CSS for the first bundle (avoids pointless extra files):
+        extract: !!options.writeMeta,
+      })
+    );
+    return config;
+  },
+};