Examine source code of Grey Sun

{
  "description": "Renders all webpages in greyscale.",
  "name": "Grey Sun",
  "manifest_version": 2,
  "version": "1.0.2",
  "homepage_url": "https://github.com/silpian/grey-sun",
  "icons": {
    "48": "icons/border-48.png",
    "96": "icons/border-96.png"
  },
  "permissions": [
    "activeTab",
    "contextMenus"
  ],
  "browser_action": {
    "default_icon": "icons/border-48.png",
    "default_title": "Greyscale for focus"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "grey_sun.js"
      ]
    }
  ]
}