chore: add build files to exports

Author: nlf

package.json

@@ -2,6 +2,10 @@
   "name": "@code4rena/typed-client",
   "version": "1.0.0",
   "main": "lib/index.js",
+  "exports": {
+    ".": "lib/index.js",
+    "./build": "lib/build/index.js"
+  },
   "types": "lib/index.d.ts",
   "files": ["lib/**/*.js", "lib/**/*.d.ts"],
   "scripts": {