Examine source code of refern clipper

{
  "manifest_version": 2,
  "name": "refern clipper",
  "description": "Save images to your refern workspace with a single click.",
  "version": "3.4",
  "icons": {
    "16": "icon-16.png",
    "32": "icon-32.png",
    "48": "icon-48.png",
    "64": "icon-64.png",
    "96": "icon-96.png",
    "128": "icon-128.png",
    "192": "icon-192.png",
    "256": "icon-256.png",
    "512": "icon-512.png",
    "1024": "icon-1024.png"
  },
  "homepage_url": "https://www.refern.app",
  "permissions": [
    "storage",
    "activeTab",
    "tabs",
    "scripting",
    "contextMenus",
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "jackson@refern.app",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_idle",
      "js": [
        "content-scripts/content.js"
      ]
    },
    {
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_start",
      "js": [
        "content-scripts/focus-guard.js"
      ],
      "world": "MAIN"
    }
  ],
  "web_accessible_resources": [
    "content-scripts/content.css"
  ],
  "browser_action": {}
}