fix: Add types fields to exports field in package.json

Author: martinnaj

package.json

@@ -50,10 +50,12 @@
   "exports": {
     ".": {
       "import": "./dist/downshift.esm.js",
-      "require": "./dist/downshift.cjs.js"
+      "require": "./dist/downshift.cjs.js",
+      "types": "./typings/index.d.ts"
     },
     "./react-native": {
-      "require": "./dist/downshift.native.cjs.js"
+      "require": "./dist/downshift.native.cjs.js",
+      "types": "./typings/index.d.ts"
     }
   },
   "keywords": [