Examine source code of Upload to imgBB

{
  "manifest_version": 2,
  "name": "Upload to imgBB",
  "version": "2.2.1",
  "description": "Right-click any image to upload it to imgBB, or capture a screen region with a preferred key combination.",
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "64": "icons/icon-64.png",
    "96": "icons/icon-96.png",
    "128": "icons/icon-128.png"
  },
  "browser_action": {
    "default_icon": {
      "16": "icons/icon-16.png",
      "32": "icons/icon-32.png",
      "48": "icons/icon-48.png"
    },
    "default_title": "Upload to imgBB"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle",
      "all_frames": true
    }
  ],
  "commands": {
    "snap-region": {
      "suggested_key": {
        "default": "Ctrl+Alt+Y"
      },
      "description": "Capture a screen region and upload it to imgBB"
    }
  },
  "permissions": [
    "menus",
    "contextMenus",
    "clipboardWrite",
    "activeTab",
    "tabs",
    "storage",
    "downloads",
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "upload-to-imgbb@extension",
      "strict_min_version": "109.0"
    }
  }
}