fix: set main module path

Author: dessant

package.json

@@ -5,6 +5,7 @@
   "author": "Armin Sebastian",
   "license": "MIT",
   "repository": "https://github.com/dessant/lock-threads",
+  "main": "src/index.js",
   "scripts": {
     "start": "probot run ./src/index.js",
     "watch": "nodemon --exec 'npm start'",