Examine source code of Media Rewind

{
  "manifest_version": 2,
  "name": "Media Rewind",
  "version": "1.7.0",
  "description": "Rewind or fast-forward any playing video/audio with custom seconds",
  "icons": {
    "48": "icons/icon48.png",
    "96": "icons/icon96.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Media Rewind"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "commands": {
    "rewind-media": {
      "suggested_key": {
        "default": "Alt+Q"
      },
      "description": "Rewind active media"
    },
    "forward-media": {
      "suggested_key": {
        "default": "Alt+W"
      },
      "description": "Forward active media"
    },
    "toggle-media": {
      "suggested_key": {
        "default": "Alt+R"
      },
      "description": "Toggle play/pause"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start",
      "all_frames": true
    }
  ],
  "permissions": [
    "activeTab",
    "storage",
    "tabs",
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "strict_min_version": "109.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      },
      "id": "{55f450ac-5802-4257-97da-717ce2fcb6a1}"
    }
  }
}