Examine source code of Font Size Decrease

{
  "manifest_version": 3,
  "short_name": "__MSG_name__",
  "homepage_url": "https://www.stefanvd.net/support/",
  "description": "__MSG_description__",
  "author": "Stefan vd",
  "icons": {
    "16": "images/icon16.png",
    "24": "images/icon24.png",
    "32": "images/icon32.png",
    "48": "images/icon48.png",
    "96": "images/icon96.png",
    "128": "images/icon128.png"
  },
  "default_locale": "en",
  "content_security_policy": {
    "extension_pages": "default-src 'none'; style-src 'self'; media-src https://www.stefanvd.net; frame-src https://www.youtube.com https://www.stefanvd.net; connect-src https://www.stefanvd.net; script-src 'self'; img-src 'self' https://www.stefanvd.net * data:; object-src 'none'"
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "version": "1.1.5",
  "name": "__MSG_name__",
  "background": {
    "scripts": [
      "scripts/constants.js",
      "scripts/background.js"
    ]
  },
  "action": {
    "default_icon": {
      "19": "images/icon19.png",
      "38": "images/icon38.png"
    },
    "default_title": "__MSG_name__"
  },
  "commands": {
    "_execute_action": {
      "suggested_key": {
        "default": "Ctrl+Shift+M",
        "mac": "MacCtrl+Shift+M"
      }
    },
    "toggle-feature-fontreset": {
      "suggested_key": {
        "default": "Ctrl+Shift+W",
        "mac": "MacCtrl+Shift+W"
      },
      "description": "__MSG_pagetitle__"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.stefanvd.net/*"
      ],
      "js": [
        "scripts/constants.js",
        "scripts/content.js"
      ]
    }
  ],
  "permissions": [
    "activeTab",
    "scripting",
    "storage",
    "contextMenus"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "fontsizedecrease@stefanvd.net",
      "strict_min_version": "113.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    },
    "gecko_android": {}
  }
}