Examine source code of Gem DevTools

{
  "$schema": "https://json.schemastore.org/chrome-manifest",
  "name" : "Gem DevTools",
  "version" : "2.3.1",
  "manifest_version" : 3 ,
  "description" : "Gem DevTools Extension to inspect and debug Gem elements",
  "devtools_page": "devtools.html",
  "browser_specific_settings": {
    "gecko": {
      "id": "{2af13fd2-a726-41de-b3a1-4bf2cb91c105}"
    }
  },
  "content_scripts" : [
    {
      "world" : "MAIN" ,
      "all_frames" : true ,
      "match_about_blank" : true ,
      "matches" : [
        "<all_urls>" 
      ],
      "js" : [
        "content.js" 
      ],
      "run_at" : "document_start" 
    }
  ],
  "icons" : {
    "512" : "logo.png"
  }
}