Examine source code of Rebrickable Refined

{
  "manifest_version": 3,
  "name": "Rebrickable Refined",
  "description": "Enhances rebrickable.com with new features and fixes some annoyances",
  "version": "1.2",
  "icons": {
    "16": "icon16.png",
    "32": "icon32.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "host_permissions": [
    "https://oprypin.github.io/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_popup": "popup.html",
    "default_title": "Rebrickable Refined"
  },
  "content_scripts": [
    {
      "matches": [
        "https://rebrickable.com/*"
      ],
      "js": [
        "settings.js",
        "global.js"
      ],
      "run_at": "document_start"
    },
    {
      "matches": [
        "https://rebrickable.com/*"
      ],
      "js": [
        "sort-order.js"
      ],
      "world": "MAIN",
      "run_at": "document_start"
    },
    {
      "matches": [
        "https://rebrickable.com/*"
      ],
      "js": [
        "common.js",
        "part-lists.js",
        "search-addition.js",
        "set-lists.js",
        "owned-colors.js"
      ],
      "run_at": "document_end"
    },
    {
      "matches": [
        "https://rebrickable.com/parts/*"
      ],
      "js": [
        "related-parts-data.js",
        "related-parts.js"
      ],
      "run_at": "document_end"
    },
    {
      "matches": [
        "https://rebrickable.com/*"
      ],
      "js": [
        "search-in-part-dialog.js"
      ],
      "world": "MAIN",
      "run_at": "document_end"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "@rebrickablerefined",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}