Examine source code of Insta-Calc

{
  "manifest_version": 3,
  "name": "InstaCalc",
  "description": "Official Automatized Calc Export for Pokemon Showdown",
  "version": "1",
  "icons": {
    "16": "/icons/16x16.png",
    "32": "/icons/32x32.png",
    "48": "/icons/48x48.png",
    "128": "/icons/128x128.png"
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false
  },
  "web_accessible_resources": [
    {
      "matches": [
        "*://play.pokemonshowdown.com/*",
        "*://*.psim.us/*"
      ],
      "resources": [
        "/scripts/instacalc.js"
      ]
    },
    {
      "matches": [
        "*://calc.pokemonshowdown.com/*"
      ],
      "resources": [
        "/scripts/calc.js"
      ]
    }
  ],
  "content_scripts": [
    {
      "matches": [
        "*://play.pokemonshowdown.com/*",
        "*://*.psim.us/*"
      ],
      "js": [
        "/shim.js"
      ]
    },
    {
      "matches": [
        "*://calc.pokemonshowdown.com/*"
      ],
      "js": [
        "/shim_calc.js"
      ]
    }
  ],
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "instacalc@mail.com"
    }
  }
}