fix: add types field to exports in package.json

resolves #495

Author: danielroe

package.json

@@ -21,6 +21,7 @@
   "sideEffects": false,
   "exports": {
     ".": {
+      "types": "./dist/index.d.ts",
       "import": "./dist/index.mjs",
       "require": "./dist/index.cjs"
     },