How to check spelling on a password-protected site?

Question

Spellchecking

Hello!
On one site, you need to check spelling, but since the site is password-protected, online services are not suitable.
I am looking for a browser extension that will check spelling on the site and highlight errors. So far I have found an extension for Chrome - LanguageTool, but it is not very convenient to use it, you must first select the text, then look for errors in a small window.