Examine source code of GaplaPlus

{
  "name": "GaplaPlus",
  "version": "1.1.1",
  "description": "The Official GaplaPlus Extension for Firefox",
  "permissions": [
    "declarativeContent",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "popup.html"
  },
  "manifest_version": 2,
  "icons": {
    "16": "./images/icon16.png",
    "32": "./images/icon32.png",
    "48": "./images/icon48.png",
    "128": "./images/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "strict_min_version": "48.0"
    }
  }
}