Add types property to package.json (ptomasroos#177)

Author: darkwebdev

package.json

@@ -3,6 +3,7 @@
   "version": "2.2.0",
   "description": "Android and iOS supported pure JS slider component with multiple markers for React Native",
   "main": "MultiSlider.js",
+  "types": "index.d.ts",
   "scripts": {
     "prettier": "prettier --single-quote --trailing-comma all --bracket-spacing --write \"**/*.js\""
   },