Examine source code of Select2Page

{
  "manifest_version": 2,
  "name": "Select2Page",
  "version": "1.1resigned1",
  "applications": {
    "gecko": {
      "id": "select@2page.com"
    }
  },
  "permissions": [
    "tabs",
    "activeTab"
  ],
  "description": "Extract current selected text and search it in google scholar (Ctl-Shift-D) or pubmed (Ctl-Shift-B) or scihb (Ctl-Shift-U)",
  "icons": {
    "48": "icons/2.png"
  },
  "background": {
    "scripts": [
      "sel2gs.js"
    ]
  },
  "commands": {
    "toggle-feature": {
      "suggested_key": {
        "default": "Ctrl+Shift+D"
      },
      "description": "Send a 'toggle-feature' event"
    },
    "toggle-feature2": {
      "suggested_key": {
        "default": "Ctrl+Shift+B"
      },
      "description": "Send a 'toggle-feature' event"
    },
    "toggle-feature3": {
      "suggested_key": {
        "default": "Ctrl+Shift+U"
      },
      "description": "Send a 'toggle-feature' event"
    }
  }
}