Examine source code of SmartSpell

{
  "manifest_version": 2,
  "name": "Smart Spell",
  "version": "3.4.0",
  "description": "Fast local Firefox spell checking with red squiggles, contextual suggestions, generic reactive-editor support, a flat correction popup, and optional single-suggestion auto-replace.",
  "browser_specific_settings": {
    "gecko": {
      "id": "smart-spell@local",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "storage",
    "menus",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "engine.js",
      "background.js"
    ],
    "persistent": true
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "content.css"
      ],
      "run_at": "document_idle",
      "all_frames": true
    }
  ],
  "incognito": "not_allowed",
  "options_ui": {
    "page": "options/options.html",
    "open_in_tab": true
  }
}