Examine source code of targetblank

{
  "manifest_version": 2,
  "version": "1.0.5",
  "name": "targetblank",
  "description": "organize your links",
  "applications": {
    "gecko": {
      "id": "extension@targetblank.org"
    }
  },
  "optional_permissions": [
    "storage"
  ],
  "chrome_url_overrides": {
    "newtab": "index.html"
  },
  "chrome_settings_overrides": {
    "homepage": "index.html"
  }
}