Examine source code of GNU LibreJS

{
  "manifest_version": 2,
  "name": "GNU LibreJS",
  "short_name": "LibreJS",
  "version": "7.21.1",
  "author": "various",
  "description": "Only allows free and/or trivial Javascript to run.",
  "applications": {
    "gecko": {
      "id": "jid1-KtlZuoiikVfFew@jetpack",
      "strict_min_version": "60.0"
    }
  },
  "icons": {
    "64": "icons/librejs.png"
  },
  "permissions": [
    "contextMenus",
    "webRequest",
    "webRequestBlocking",
    "activeTab",
    "notifications",
    "sessions",
    "storage",
    "tabs",
    "<all_urls>"
  ],
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "64": "icons/librejs.png"
    },
    "default_title": "LibreJS",
    "default_popup": "html/display_panel/content/display-panel.html"
  },
  "options_ui": {
    "page": "html/preferences_panel/preferences_panel.html",
    "open_in_tab": true
  },
  "web_accessible_resources": [
    "html/report_page/report.html"
  ],
  "background": {
    "scripts": [
      "bundle.js"
    ]
  },
  "content_scripts": [
    {
      "run_at": "document_start",
      "matches": [
        "<all_urls>"
      ],
      "match_about_blank": true,
      "all_frames": true,
      "js": [
        "content/externalLicenseChecker.js"
      ]
    }
  ]
}