Examine source code of OpenHeader

{
  "manifest_version" : 3 ,
  "name" : "OpenHeader",
  "version" : "1.0.0",
  "description" : "A lightweight open-source extension to modify request and response headers and filter by URL regexes.",
  "icons" : {
    "16" : "icons/icon16.png",
    "32" : "icons/icon32.png",
    "48" : "icons/icon48.png",
    "128" : "icons/icon128.png"
  },
  "permissions" : [
    "storage" ,
    "tabs" ,
    "declarativeNetRequest" 
  ],
  "host_permissions" : [
    "*://*/*" 
  ],
  "action" : {
    "default_icon" : {
      "16" : "icons/icon16.png",
      "32" : "icons/icon32.png",
      "48" : "icons/icon48.png",
      "128" : "icons/icon128.png"
    },
    "default_title" : "OpenHeader",
    "default_popup" : "popup.html"
  },
  "background" : {
    "service_worker" : "background.js" ,
    "scripts" : [
      "background.js" 
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "openheader@kevinchua6",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}