Examine source code of Session Hold

{
  "manifest_version": 2,
  "name": "Session Hold",
  "version": "1.1.0",
  "description": "Save a browsing session for later.",
  "homepage_url": "https://github.com/Stevox404/session-hold",
  "icons": {
    "48": "icons/save-icon-48.png",
    "96": "icons/save-icon-96.png"
  },
  "permissions": [
    "bookmarks",
    "tabs"
  ],
  "browser_action": {
    "browser_style": true,
    "default_icon": "icons/save-icon-96.png",
    "default_title": "Session Hold",
    "default_popup": "popup/index.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "strict_min_version": "52.0"
    }
  }
}