fix: enable TypeScript declaration file generation

Add dts: true to tsup config to generate .d.ts files.
Fixes missing type definitions in published package.

Fixes #13

Author: mgcrea

tsup.config.ts

@@ -5,4 +5,5 @@ export default defineConfig({
   format: ["cjs", "esm"],
   sourcemap: true,
   clean: true,
+  dts: true,
 });