Examine source code of BetterTitle+

{
  "manifest_version": 2,
  "name": "BetterTitle+",
  "description": "Change title of the current tab with 2 clicks",
  "version": "1.0",
  "icons": {
    "48": "./img/smallesticon.png",
    "96": "./img/smallicon.png"
  },
  "applications": {
    "gecko": {
      "id": "bettertitleplus@kwiatekmiki.pl",
      "strict_min_version": "62.0"
    }
  },
  "web_accessible_resources": [
    "changeTitle.js"
  ],
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "BetterTitle+"
  }
}