Update bower.json

bower.json

 {
   "name": "bags",
-  "version": "1.0.1",
   "homepage": "https://cornernote.github.io/minetest-bags/",
   "description": "Attach bags to your inventory to increase item storage capacity.",
-  "main": "init.lua",
+  "screenshots": [
+    "http://cornernote.github.io/minetest-bags/img/screenshot.png"
+  ],
   "keywords": [
     "bags"
   ],