Examine source code of One2Tree

{
  "manifest_version": 2,
  "name": "One2Tree",
  "version": "1.4.3",
  "description": "Views the pedigree tree in an interactive ahnentafel list and pedigree chart. It works on Ancestry, MyHeritage and FamilyTreeDNA.",
  "author": "NordeboApps",
  "browser_specific_settings": {
    "gecko": {
      "id": "{9cc3da74-c2eb-4170-be47-69da56a654dd}"
    }
  },
  "permissions": [
    "tabs",
    "webRequest",
    "identity",
    "storage",
    "https://nordeboapps.com/*",
    "https://tree.familytreedna.com/*",
    "https://treeapi.familytreedna.com/*",
    "https://www.ancestry.com/*",
    "https://www.ancestry.co.uk/*",
    "https://www.ancestry.ca/*",
    "https://www.ancestry.com.au/*",
    "https://www.ancestry.de/*",
    "https://www.ancestry.it/*",
    "https://www.ancestry.fr/*",
    "https://www.ancestry.se/*",
    "https://www.ancestry.mx/*",
    "https://www.myheritage.com/*",
    "https://www.myheritage.cat/*",
    "https://www.myheritage.cz/*",
    "https://www.myheritage.dk/*",
    "https://www.myheritage.de/*",
    "https://www.myheritage.ee/*",
    "https://www.myheritage.es/*",
    "https://www.myheritage.fr/*",
    "https://www.myheritage.co.kr/*",
    "https://www.myheritage.com.hr/*",
    "https://www.myheritage.it/*",
    "https://www.myheritage.lv/*",
    "https://www.myheritage.lt/*",
    "https://www.myheritage.hu/*",
    "https://www.myheritage.nl/*",
    "https://www.myheritage.jp/*",
    "https://www.myheritage.no/*",
    "https://www.myheritage.pl/*",
    "https://www.myheritage.com.br/*",
    "https://www.myheritage.com.pt/*",
    "https://www.myheritage.ro/*",
    "https://www.myheritage.mk/*",
    "https://www.myheritage.sk/*",
    "https://www.myheritage.si/*",
    "https://www.myheritage.fi/*",
    "https://www.myheritage.se/*",
    "https://www.myheritage.com.tr/*",
    "https://www.myheritage.cn/*",
    "https://www.myheritage.tw/*",
    "https://www.myheritage.gr/*",
    "https://www.myheritage.rs/*",
    "https://www.myheritage.com.ua/*",
    "https://www.myheritage.am/*",
    "https://www.myheritage.co.il/*",
    "https://www.myheritage.co.in/*",
    "https://accounts.google.com/*",
    "https://www.googleapis.com/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_title": "One2Tree",
    "default_popup": "action.html",
    "default_icon": {
      "32": "32.png",
      "64": "64.png",
      "128": "128.png"
    }
  },
  "icons": {
    "32": "32.png",
    "64": "64.png",
    "128": "128.png"
  }
}