Examine source code of Explainshell Addon

{
  "manifest_version": 2,
  "name": "ExplainShell Search Plugin",
  "description": "Allows the user to search selected text on a webpage directly on ExplainShell",
  "version": "1.1resigned1",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "contextMenus",
    "activeTab"
  ],
  "icons": {
    "16": "icons/explain-16.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "@explainshell-plugin"
    }
  }
}