Examine source code of Annotating the Web

{
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "16": "assets/icon_16.png",
      "38": "assets/icon_38.png"
    }
  },
  "applications": {
    "gecko": {
      "id": "@mywebannotator",
      "strict_min_version": "57.0"
    }
  },
  "content_scripts": [
    {
      "all_frames": false,
      "css": [
        "data/css/annotator.css"
      ],
      "js": [
        "data/js/vendor/jquery-3.4.1.js",
        "data/js/pkg/annotator-full.js",
        "data/js/pkg/annotator.markdown.js",
        "data/js/pkg/annotator.offline.js",
        "data/js/pkg/showdown.js",
        "data/js/add-annotation.js"
      ],
      "exclude_matches": [
        "*://*.youtube.com/*",
        "*://calendar.google.com/*",
        "*://docs.google.com/*",
        "*://*.whatsapp.com/*",
        "*://*.google.com/maps/*"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "description": "Add-on, by Mediamaster.eu, to easily add annotation functionality to any webpage",
  "developer": {
    "name": "ulmdesign"
  },
  "homepage_url": "https://mediamaster.eu/contatti",
  "icons": {
    "16": "assets/icon_16.png",
    "128": "assets/icon_128.png"
  },
  "manifest_version": 2,
  "name": "Annotating the Web",
  "permissions": [
    "<all_urls>",
    "tabs",
    "notifications"
  ],
  "short_name": "Simply select text of webpage and make a comment clicking on related icon",
  "version": "1.3.0",
  "web_accessible_resources": [
    "data/images/*.png"
  ]
}