Examine source code of Ream - Reader Mode

{
  "manifest_version": 3,
  "name": "Ream",
  "description": "Reader mode extension",
  "version": "0.0.4",
  "icons": {
    "16": "icon-16.png",
    "24": "icon-24.png",
    "48": "icon-48.png",
    "96": "icon-96.png",
    "128": "icon-128.png"
  },
  "permissions": [
    "activeTab",
    "storage",
    "scripting"
  ],
  "action": {},
  "omnibox": {
    "keyword": "ream"
  },
  "web_accessible_resources": [
    {
      "resources": [
        "content-scripts/content.js"
      ],
      "matches": [
        "<all_urls>"
      ]
    },
    {
      "resources": [
        "content-scripts/content.css"
      ],
      "matches": [
        "<all_urls>"
      ]
    },
    {
      "resources": [
        "content-scripts/content.css"
      ],
      "matches": []
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "ream@ream.zsheng.app"
    }
  },
  "commands": {
    "_execute_action": {
      "suggested_key": {
        "default": "Ctrl+Shift+Y",
        "mac": "Command+Shift+Y"
      }
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": []
}