Examine source code of WebCiv Extension

{
  "manifest_version": 2,
  "name": "WebCiv Extension",
  "version": "0.92resigned1",
  "description": "WebCiv overview map grabber. Author: Krešimir Ižaković, 2017.",
  "icons": {
    "48": "icon20.png"
  },
  "background": {
    "scripts": [
      "WebCivMapBackground.js"
    ]
  },
  "options_page": "",
  "permissions": [
    "activeTab",
    "tabs",
    "webRequest",
    "*://play.freeciv.org/webclient/*"
  ],
  "browser_action": {
    "default_title": "WebCiv Extension",
    "default_icon": "icon20.png",
    "default_popup": "PopUp.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://play.freeciv.org/webclient/*"
      ],
      "js": [
        "WebCivMap.js"
      ],
      "all_frames": true
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{6c716b07-c162-4a46-86df-304b209fffb6}"
    }
  }
}