Merge pull request #31 from swup/fix/declaration-file-package-json

Author: hirasso

package.json

@@ -8,6 +8,7 @@
   "main": "./dist/index.cjs",
   "module": "./dist/index.module.js",
   "unpkg": "./dist/index.umd.js",
+  "types": "./dist/index.d.ts",
   "exports": {
     ".": {
       "types": "./dist/index.d.ts",