Examine source code of H2K

{
  "manifest_version": 2,
  "name": "H2K",
  "description": "Converts text on a webpage between hiragana and katakana.",
  "version": "1.2.2",
  "background": {
    "scripts": [
      "browser-polyfill.min.js",
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/h2k-48.png",
    "default_title": "H2K",
    "default_popup": "popup.html"
  },
  "commands": {
    "convert": {
      "suggested_key": {
        "default": "Ctrl+Shift+U"
      },
      "description": "Run the conversion on the webpage"
    },
    "reload_disabled": {
      "suggested_key": {
        "default": "Ctrl+Shift+V"
      },
      "description": "Reload the webpage without converting"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "browser-polyfill.min.js",
        "h2k.js"
      ]
    }
  ],
  "icons": {
    "16": "icons/h2k-16.png",
    "48": "icons/h2k-48.png",
    "128": "icons/h2k-128.png"
  },
  "options_ui": {
    "page": "options.html",
    "chrome_style": false,
    "open_in_tab": true
  },
  "permissions": [
    "storage"
  ]
}