Examine source code of fera

{
  "manifest_version": 3,
  "name": "Fera",
  "version": "1.2",
  "description": "Send articles to your e-reader via Instapaper",
  "browser_specific_settings": {
    "gecko": {
      "id": "extension@readfera.com",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "browsingActivity"
        ],
        "optional": [
          "technicalAndInteraction"
        ]
      }
    }
  },
  "permissions": [
    "activeTab",
    "scripting",
    "storage"
  ],
  "host_permissions": [
    "https://article-editor-3522884104.europe-west3.run.app/*"
  ],
  "icons": {
    "16": "fera-icon-16.png",
    "48": "fera-icon-48.png",
    "128": "fera-icon-128.png"
  },
  "action": {
    "default_icon": {
      "16": "fera-icon-16.png",
      "48": "fera-icon-48.png",
      "128": "fera-icon-128.png"
    },
    "default_title": "Send to e-reader"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://readfera.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ]
}