feat: export TS types (#350)

`mount` and `mountCallback` exported functions should have IntelliSense now

Author: bahmutov

package.json

@@ -17,6 +17,7 @@
   ],
   "license": "MIT",
   "main": "dist/index.js",
+  "types": "dist",
   "publishConfig": {
     "registry": "http://registry.npmjs.org/"
   },