Examine source code of Fluis extension

{
  "name": "Fluis extension",
  "version": "2.0.0",
  "manifest_version": 2,
  "description": "Fluis extension",
  "applications": {
    "gecko": {
      "id": "extension@fluis.com"
    }
  },
  "icons": {
    "512": "images/app_icon512.png"
  },
  "browser_action": {
    "default_icon": "images/logo512.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "css": [
        "/css/external.css"
      ]
    }
  ],
  "web_accessible_resources": [
    "fluis.html",
    "static/css/app.css",
    "images/icons/burger.svg",
    "images/logo_white.svg",
    "images/logo_blue.svg",
    "images/logo64.png",
    "images/logo512.png",
    "images/icons/toolbar/draw.svg",
    "images/icons/toolbar/edit.svg",
    "images/icons/toolbar/element.svg",
    "images/icons/toolbar/move.svg",
    "images/icons/toolbar/square.svg",
    "images/icons/draw/size1.svg",
    "images/icons/draw/size2.svg",
    "images/icons/draw/size3.svg",
    "images/icons/draw/save.svg",
    "images/icons/draw/cancel.svg",
    "images/icons/tabs/dashboard.svg",
    "images/icons/tabs/chat.svg",
    "images/icons/tabs/annotations.svg",
    "images/icons/tabs/settings.svg",
    "images/icons/toolbar/toolbar.svg",
    "images/icons/toolbar/scenario.svg",
    "images/icons/mouse/blue.svg",
    "images/icons/mouse/green.svg",
    "images/icons/mouse/red.svg",
    "images/icons/mouse/violet.svg",
    "images/icons/mouse/yellow.svg"
  ],
  "permissions": [
    "activeTab",
    "storage",
    "webNavigation",
    "tabs",
    "http://*/",
    "https://*/"
  ]
}