Examine source code of ProtonMail (unofficial)

{
  "manifest_version": 2,
  "name": "__MSG_extension_name__",
  "version": "1.10.0",
  "description": "__MSG_extension_description__",
  "homepage_url": "https://github.com/gitladen7/protonmail-webextension",
  "default_locale": "en",
  "icons": {
    "16": "icons/icon.svg",
    "48": "icons/icon.svg",
    "96": "icons/icon.svg"
  },
  "permissions": [
    "https://mail.protonmail.com/*",
    "https://old.protonmail.com/*",
    "https://beta.protonmail.com/*",
    "https://app.protonmail.ch/*",
    "https://protonirockerxow.onion/*",
    "tabs",
    "storage",
    "cookies",
    "notifications",
    "webRequest",
    "alarms"
  ],
  "browser_action": {
    "browser_style": false,
    "default_popup": "index.html",
    "default_icon": "icons/icon.svg",
    "default_title": "ProtonMail",
    "theme_icons": [
      {
        "light": "icons/icon-light.svg",
        "dark": "icons/icon.svg",
        "size": 32
      }
    ]
  },
  "background": {
    "scripts": [
      "browser-polyfill.js",
      "background.js"
    ]
  },
  "content_security_policy": "default-src 'self'; connect-src https://mail.protonmail.com/api/events/ https://mail.protonmail.com/api/messages/count https://mail.protonmail.com/api/messages https://mail.protonmail.com/api/messages/read https://mail.protonmail.com/api/settings/mail https://mail.protonmail.com/api/auth/refresh https://old.protonmail.com/api/events/ https://old.protonmail.com/api/messages/count https://old.protonmail.com/api/messages https://old.protonmail.com/api/messages/read https://old.protonmail.com/api/settings/mail https://old.protonmail.com/api/auth/refresh https://beta.protonmail.com/api/events/ https://beta.protonmail.com/api/messages/count https://beta.protonmail.com/api/messages https://beta.protonmail.com/api/messages/read https://beta.protonmail.com/api/settings/mail https://beta.protonmail.com/api/auth/refresh https://app.protonmail.ch/api/events/ https://app.protonmail.ch/api/messages/count https://app.protonmail.ch/api/messages https://app.protonmail.ch/api/messages/read https://app.protonmail.ch/api/settings/mail https://app.protonmail.ch/api/auth/refresh https://protonirockerxow.onion/api/events/ https://protonirockerxow.onion/api/messages/count https://protonirockerxow.onion/api/messages https://protonirockerxow.onion/api/messages/read https://protonirockerxow.onion/api/settings/mail https://protonirockerxow.onion/api/auth/refresh"
}