Examine source code of Pinyin Annotator

{
  "icons": {
    "16": "icon16.plasmo.2577fc03.png",
    "32": "icon32.plasmo.d583dc1e.png",
    "48": "icon48.plasmo.e0fcfb1d.png",
    "64": "icon64.plasmo.e6259081.png",
    "128": "icon128.plasmo.96a1ede9.png"
  },
  "manifest_version": 3,
  "action": {
    "default_icon": {
      "16": "icon16.plasmo.2577fc03.png",
      "32": "icon32.plasmo.d583dc1e.png",
      "48": "icon48.plasmo.e0fcfb1d.png",
      "64": "icon64.plasmo.e6259081.png",
      "128": "icon128.plasmo.96a1ede9.png"
    },
    "default_popup": "popup.html"
  },
  "version": "1.6.1",
  "author": "fixicelo <fixicelo@gmail.com>",
  "name": "Pinyin Annotator",
  "description": "A browser extension overlays Hanyu Pinyin annotations over Chinese characters present in web pages and video closed captions.",
  "background": {
    "scripts": [
      "static/background/index.js"
    ]
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "permissions": [
    "storage",
    "activeTab",
    "scripting",
    "contextMenus"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "all-urls.0c96cbd5.js"
      ],
      "css": []
    },
    {
      "matches": [
        "*://www.youtube.com/*"
      ],
      "js": [
        "youtube.89398776.js"
      ],
      "all_frames": true,
      "css": []
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "pinyin-annotator@fixicelo.ext"
    }
  },
  "commands": {
    "toggle-annotation": {
      "suggested_key": {
        "default": "Alt+Shift+P",
        "mac": "Alt+Shift+P"
      },
      "description": "Toggle Pinyin annotations"
    }
  }
}