Examine source code of SupaFill

{
  "manifest_version": 2,
  "name": "SupaFill",
  "description": "Fill everything in a snap.",
  "version": "1.4.3",
  "icons": {
    "16": "icon/16.png",
    "32": "icon/32.png",
    "48": "icon/48.png",
    "96": "icon/96.png",
    "128": "icon/128.png"
  },
  "permissions": [
    "activeTab",
    "contextMenus",
    "storage"
  ],
  "commands": {
    "fill-all-forms": {
      "suggested_key": {
        "default": "Ctrl+Shift+E",
        "mac": "Command+Shift+E"
      },
      "description": "Fill all forms on the page"
    },
    "clear-all-fields": {
      "suggested_key": {
        "default": "Ctrl+Shift+L",
        "mac": "Command+Shift+L"
      },
      "description": "Clear all fields on the page"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "supafill@example.com",
      "strict_min_version": "115.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": [
          "personallyIdentifyingInfo",
          "personalCommunications",
          "websiteActivity"
        ]
      }
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "SupaFill",
    "default_popup": "popup.html"
  },
  "options_ui": {
    "open_in_tab": true,
    "page": "options.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "all_frames": true,
      "js": [
        "content-scripts/content.js"
      ]
    }
  ]
}