update: move index.js to src

Author: kartikkhk

package.json

@@ -2,7 +2,7 @@
   "name": "kartik1998@queue-manager",
   "version": "1.0.0",
   "description": "A wrapper over async queue helpful in managing the queue length.",
-  "main": "index.js",
+  "main": "src/index.js",
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1"
   },