Examine source code of tabclip

{
  "manifest_version": 2,
  "name": "tabclip",
  "description": "Copy browser tabs to (or create them from) your clipboard.",
  "version": "1.4",
  "author": "Josh Dick",
  "icons": {
    "16": "img/tabclip_16.png",
    "32": "img/tabclip_32.png",
    "48": "img/tabclip_48.png",
    "128": "img/tabclip_128.png"
  },
  "homepage_url": "https://joshdick.github.io/tabclip",
  "browser_action": {
    "default_icon": "img/tabclip_128.png",
    "default_popup": "popup.htm",
    "default_title": "tabclip"
  },
  "background": {
    "page": "background.htm"
  },
  "commands": {
    "copy-tabs": {
      "suggested_key": {
        "default": "Ctrl+Shift+C",
        "mac": "MacCtrl+Shift+C"
      },
      "description": "Copy tab(s) to the clipboard"
    },
    "paste-tabs": {
      "suggested_key": {
        "default": "Ctrl+Shift+V",
        "mac": "MacCtrl+Shift+V"
      },
      "description": "Paste tab(s) from the clipboard"
    }
  },
  "permissions": [
    "clipboardRead",
    "clipboardWrite",
    "notifications",
    "storage",
    "tabs"
  ],
  "content_security_policy": "script-src 'self'; object-src 'self'"
}