Examine source code of Extend Text Selection

{
  "manifest_version": 3,
  "name": "Extend Text Selection",
  "description": "__MSG_extensionDescription__",
  "default_locale": "en",
  "version": "0.0.1",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "activeTab",
    "scripting",
    "contextMenus"
  ],
  "icons": {
    "48": "icon.svg",
    "96": "icon.svg",
    "128": "icon.svg"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "extend_text_selection@emvaized.dev"
    }
  },
  "commands": {
    "extend-text-selection": {
      "suggested_key": {
        "default": "Ctrl+Alt+A"
      },
      "description": "__MSG_extendTextSelection__"
    }
  }
}