Examine source code of tab-closer-plus

{
  "browser_specific_settings": {
    "gecko": {
      "strict_min_version": "58.0a1",
      "id": "{845e89b8-0c2e-40bb-a68a-b1c959da8d1c}"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "browser_style": true,
    "default_title": "Closse tab"
  },
  "description": "Close tab if URL is in a list of URLs",
  "manifest_version": 2,
  "name": "Close tab",
  "permissions": [
    "tabs"
  ],
  "version": "1.1",
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  }
}