Subscribe to comments plugin without .js or .css files?

I’m looking for a super simple lightweight WP plugin to add a checkbox where commenters can (subscribe to comments) select to be notified of followup comments to the blog post. However, looking for a plugin that uses no .js and possibly no .css files.

For example I needed a plugin for contact form that used no .js files and I found this one:
https://ww.wp.xz.cn/plugins/simple-basic-contact-form/

Now I just need something similar that does not load up the site with any .js files or .css files.

Thanks!