Examine source code of Grayscale Browsing

{
  "manifest_version": 2,
  "name": "Grayscale Browsing",
  "version": "1.3resigned1",
  "description": "Toggle grayscale on the active tab for the ultimate reading experience",
  "icons": {
    "48": "icons/icon_on.png"
  },
  "permissions": [
    "tabs"
  ],
  "browser_action": {
    "default_icon": "icons/icon_off.png",
    "browser_style": true
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content-script.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{9b0552d7-b08e-49d4-a0d9-f03121b8f4a5}"
    }
  }
}