Examine source code of Metric Beyond

{
  "manifest_version": 2,
  "name": "Metric Beyond",
  "description": "Bring the metric unit system to D&D Beyond!",
  "version": "1.9.4",
  "icons": {
    "256": "images/Metric_Beyond_256.png",
    "512": "images/Metric_Beyond_512.png"
  },
  "content_scripts": [
    {
      "js": [
        "libs/purify.min.js",
        "content.js"
      ],
      "matches": [
        "https://www.dndbeyond.com/characters/*",
        "https://www.dndbeyond.com/monsters/*",
        "https://www.dndbeyond.com/magic-items/*",
        "https://www.dndbeyond.com/spells/*",
        "https://www.dndbeyond.com/sources/*",
        "https://www.dndbeyond.com/encounters/*",
        "https://www.dndbeyond.com/combat-tracker/*"
      ]
    }
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "32": "images/toolbar_MB_32.png",
      "38": "images/toolbar_MB_38.png",
      "48": "images/toolbar_MB_48.png",
      "72": "images/toolbar_MB_72.png"
    },
    "default_title": "Metric Beyond"
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{8902ef2d-31fe-4223-b4fe-81824ca77ed9}"
    }
  }
}