Add types to exports

Author: eliot-akira

package.json

@@ -16,7 +16,8 @@
   "exports": {
     ".": {
       "import": "./index.js",
-      "require": "./index.cjs"
+      "require": "./index.cjs",
+      "types": "./index.d.ts"
     }
   },
   "author": {