Examine source code of FX OSK

{
  "manifest_version": 2,
  "name": "FX OSK",
  "version": "1.12.0",
  "description": "On-Screen Keyboard for FireFox",
  "icons": {
    "48": "icon.svg",
    "96": "icon.svg"
  },
  "background": {
    "scripts": [
      "kb.js"
    ]
  },
  "content_scripts": [
    {
      "all_frames": true,
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "keyboard.js"
      ],
      "run_at": "document_end"
    }
  ],
  "permissions": [
    "webRequest",
    "tabs",
    "storage",
    "activeTab",
    "<all_urls>",
    "webNavigation"
  ],
  "options_ui": {
    "page": "options/osk_settings.html",
    "browser_style": true
  }
}