Examine source code of HTMaiL: Insert HTML

{
  "version": "7.6.0",
  "manifest_version": 2,
  "name": "HTMaiL: Insert HTML",
  "description": "HTMaiL: Insert HTML into Gmail, Outlook and Yahoo Mail",
  "default_locale": "en",
  "author": "dziul <dziul@gmail.com>",
  "icons": {
    "128": "src/assets/images/ico@128.png",
    "256": "src/assets/images/ico@256.png"
  },
  "permissions": [
    "storage",
    "tabs",
    "management",
    "https://mail.google.com/*",
    "https://inbox.google.com/*",
    "https://mail.yahoo.com/*",
    "https://*.mail.yahoo.com/*",
    "https://outlook.live.com/*",
    "https://outlook.office.com/*"
  ],
  "background": {
    "scripts": [
      "service-worker-loader.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_title": "HTMaiL: Insert HTML"
  },
  "content_scripts": [
    {
      "js": [
        "assets/index.tsx-loader.5f8d8963.js"
      ],
      "matches": [
        "https://mail.google.com/*",
        "https://inbox.google.com/*"
      ],
      "css": [
        "assets/error-boundary.766d1078.css",
        "assets/index.90b8548b.css"
      ]
    },
    {
      "js": [
        "assets/index.tsx-loader.675984bc.js"
      ],
      "matches": [
        "https://mail.yahoo.com/*",
        "https://*.mail.yahoo.com/*"
      ],
      "css": [
        "assets/error-boundary.766d1078.css",
        "assets/index.bc6adaf3.css"
      ]
    },
    {
      "js": [
        "assets/index.tsx-loader.70bc4b11.js"
      ],
      "matches": [
        "https://outlook.live.com/*",
        "https://outlook.office.com/*"
      ],
      "css": [
        "assets/error-boundary.766d1078.css",
        "assets/index.35862c7c.css"
      ]
    }
  ],
  "web_accessible_resources": [
    "assets/use-message.7c43ef76.js",
    "assets/error-boundary.bd8e3851.js",
    "assets/index.tsx.fc0d0b8f.js",
    "assets/index.tsx.e3d20352.js",
    "assets/index.tsx.8b1a4ee5.js"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{e48b7aaa-2174-4b31-bf46-135398346cbb}"
    }
  }
}