Examine source code of GitHub Contribution Color Graph

{
  "name" : "GitHub Contribution Color Graph",
  "description" : "Change colors of contribution graph in GitHub",
  "manifest_version" : 2 ,
  "version" : "1.7.2",
  "applications": {
    "gecko": {
      "strict_min_version": "57.0",
      "id": "github-contribution-color-graph@example.com"
    }
  },
  "content_scripts" : [
    {
      "js" : [
        "js/contentscript.js" 
      ],
      "matches" : [
        "https://github.com/*" 
      ],
      "run_at" : "document_end" 
    }
  ],
  "options_ui" : {
    "page": "options.html" ,
    "open_in_tab": true
  },
  "permissions" : [
    "storage" 
  ],
  "icons" : {
    "48" : "images/icon-48.png"
  }
}