Add types definition file to package.json

Author: SPodjasek

package.json

@@ -16,6 +16,7 @@
     "url": "https://github.com/mongodb-js/mongodb-connection-string-url/issues"
   },
   "main": "lib/index.js",
+  "types": "lib/index.d.ts",
   "exports": {
     "require": "./lib/index.js",
     "import": "./.esm-wrapper.mjs"