Examine source code of Streaming+ sequencer

{
  "manifest_version": 3,
  "name": "Streaming+ sequencer",
  "version": "1.3.2",
  "description": "Streaming+にシーケンスボタンを追加します",
  "icons": {
    "48": "icons/icon48.png",
    "96": "icons/icon96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://live.eplus.jp/*"
      ],
      "js": [
        "content_scripts/index.js"
      ],
      "css": [
        "content_scripts/style.css"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "streaming-plus-sequencer@windyakin.net"
    }
  }
}