fix main in package.json

Author: rgrassian-split

package.json

@@ -17,7 +17,7 @@
   "bugs": "https://github.com/splitio/openfeature-split-provider-js/issues",
   "license": "Apache-2.0",
   "author": "Josh Sirota <[email protected]>",
-  "main": "src/index.js",
+  "main": "src/index.ts",
   "types": "types",
   "engines": {
     "npm": ">=3",