fix: add express to tsup config

Author: aj-may

tsup.config.ts

@@ -1,7 +1,7 @@
 import { defineConfig } from "tsup";
 
 export default defineConfig({
- entry: ["src/index.ts", "src/next/index.ts", "src/rainbowkit/index.tsx"],
+ entry: ["src/index.ts", "src/next/index.ts", "src/express/index.tsx"],
  splitting: false,
  sourcemap: true,
  dts: true,