🔧(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/tsconfig.eslint.json

@@ -0,0 +1,8 @@
+{
+  "extends": "./tsconfig.json",
+  "exclude": [],
+  "include": [
+    "**/*.ts",
+    "**/*.tsx"
+  ]
+}