spellcheck: true !important;

I would like to force spellcheck for all websites, and override any HTML code from the websites. which may be disabling it. This should be done automatically and not by inspecting and manually altering the HTML. I consulted with ChatGPT and tried adding some code to my existing userChrome.css but it is having no effect, even after clearing cache and restarting Firefox. For instance, faxzero.com has a form with spellcheck disabled. I tinkered with the CSS and kept testing faxzero, but the spellcheck always remains disabled. How can I accomplish my goal? Code: body[spellcheck="false"], input[type="text"][spellcheck="false"], input[type="email"][spellcheck="false"], input[type="password"][spellcheck="false"], input[type="search"][spellcheck="false"], input[type="url"][spellcheck="false"], textarea[spellcheck="false"], [contenteditable="true"][spellcheck="false"] { spellcheck: true !important; }