Examine source code of FontFlow

{
  "manifest_version": 2,
  "name": "FontFlow",
  "version": "1.0.2",
  "description": "Customize fonts on any webpage. Built for dyslexia, ADHD, and everyone who wants to read comfortably.",
  "author": "Orange",
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "browser_action": {
    "default_popup": "popup.firefox.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    },
    "default_title": "FontFlow - Customize Fonts"
  },
  "permissions": [
    "storage",
    "activeTab",
    "tabs",
    "<all_urls>"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.firefox.js"
      ],
      "run_at": "document_end"
    }
  ],
  "background": {
    "scripts": [
      "background.firefox.js"
    ],
    "persistent": false
  },
  "web_accessible_resources": [
    "fonts/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "fontflow@orange",
      "strict_min_version": "109.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  }
}