fix: Add types to exports in package.json (#111)

Author: SimenB

package.json

@@ -21,6 +21,7 @@
   "types": "index.d.ts",
   "exports": {
     ".": {
+      "types": "./index.d.ts",
       "import": "./index.js",
       "require": "./umd/index.js"
     }