Examine source code of Base64 Selection Decoder

{
  "manifest_version": 2,
  "name": "Base64 Selection Decoder",
  "version": "1.0",
  "description": "Decodes Base64-encoded text selections and copies the decoded text to the clipboard.",
  "permissions": [
    "contextMenus",
    "clipboardWrite",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "applications": {
    "gecko": {
      "id": "@selection-decoder"
    }
  },
  "icons": {
    "16": "icons/icon.svg",
    "48": "icons/icon.svg",
    "128": "icons/icon.svg"
  }
}