fix: add CJS build for NestJS CommonJS compatibility

NestJS compiles to CommonJS, but the package only exported ESM.
Node throws ERR_PACKAGE_PATH_NOT_EXPORTED when CJS code requires
an ESM-only package. Added dual ESM/CJS build with proper exports
conditions.

- ESM output in dist/esm/, CJS output in dist/cjs/
- package.json exports now includes import, require, and default
- Bumped to 0.1.1

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tsconfig.build.json

@@ -1,4 +1,7 @@
 {
   "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "outDir": "./dist/esm"
+  },
   "exclude": ["node_modules", "dist", "tests", "**/*.test.ts"]
 }