Examine source code of New Tab (next to active one) Button

{
  "manifest_version": 3,
  "name": "New Tab (next to active one) Button",
  "author": "David \"Kravimir\" S.",
  "version": "1.5",
  "short_name": "New Tab",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "description": "A button for the toolbar to open a new tab immediately after or before the current tab. Also has a context menu option on the extension icon to close the active tab in the window. (The extension icon color can be changed in the options; great for use with dark themes.)",
  "icons": {
    "16": "icons/new-tab-icon16.png",
    "32": "icons/new-tab-icon32.png",
    "48": "icons/new-tab-icon48.png",
    "128": "icons/new-tab-icon128.png"
  },
  "web_accessible_resources": [
    {
      "resources": [
        "data:image/svg+xml,%3Csvg viewBox='0 0 32 32' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath d='m3.572 1c-0.907538 2.548e-4 -2.54542 1.66446-2.572 2.572v27.428h1.5v-25.951c0.0108763-1.1874 1.19032-2.56453 2.365-2.54906h22.27c1.27506 0.037162 2.35991 1.30414 2.36496 2.54906v25.951h1.5v-27.428c0.026061-0.933844-1.66443-2.57174-2.57196-2.572z' fill='%234537FF'/%3E%3Cpath d='m17.4696 5.011 0.0056 9.64571 9.52478 0.0055v2.81163l-9.52478 0.0055-0.0055 9.52478h-2.81163l-0.0055-9.52478-9.65259-0.0056-3e-7 -2.81148 9.65259-0.0056 0.07627-9.64562z' fill='%234537ff'/%3E%3C/svg%3E"
      ],
      "matches": [
        "*://*/*"
      ]
    }
  ],
  "action": {},
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false
  },
  "permissions": [
    "storage",
    "contextMenus",
    "activeTab"
  ],
  "optional_permissions": [
    "clipboardRead",
    "management"
  ],
  "commands": {
    "duplicateTabURLOnly": {
      "description": "Duplicate Tab (Location Only)"
    },
    "newTab": {
      "description": "Open new tab adjacent to the current one."
    },
    "newTabAltSide": {
      "description": "Open new tab on opposite side, adjacent to the current one."
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "new_tab@dynamicsitesolutions.com",
      "strict_min_version": "109.0"
    },
    "gecko_android": {
      "strict_min_version": "120.0"
    }
  }
}