🔧(demo) update demo app to ts config file, customize one token

Showcase a situation where we want to customize a component's design token.

apps/demo/cunningham.ts

@@ -0,0 +1,12 @@
+export default {
+  theme: {
+    colors: {
+      primary: "purple",
+    },
+  },
+  components: {
+    button: {
+      "border-radius": "30px",
+    },
+  },
+};