Examine source code of Mouseless

{
  "manifest_version": 2,
  "name": "Mouseless",
  "version": "0.13.0",
  "description": "Quick keyboard access to links and other interactive elements",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "ext/content.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "ext/background.js"
    ]
  },
  "options_ui": {
    "page": "settings/options.html"
  },
  "icons": {
    "32": "assets/icon-32.png",
    "48": "assets/icon-48.png",
    "64": "assets/icon-64.png",
    "128": "assets/icon-128.png"
  },
  "browser_action": {
    "default_icon": {
      "32": "assets/icon-32.png",
      "48": "assets/icon-48.png",
      "64": "assets/icon-64.png",
      "128": "assets/icon-128.png"
    }
  },
  "applications": {
    "gecko": {
      "id": "@mouseless"
    }
  },
  "permissions": [
    "clipboardWrite",
    "tabs",
    "storage"
  ]
}