Examine source code of Close Tabs to the Left

{
  "applications": {
    "gecko": {
      "strict_min_version": "53.0",
      "id": "{08fb86c7-5590-40b1-ba0f-22917b9a5faf}"
    }
  },
  "description": "__MSG_extensionDescription__",
  "homepage_url": "https://github.com/mkopec/close-tabs-to-the-left",
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "version": "1.4.2resigned1",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "contextMenus"
  ],
  "default_locale": "en"
}