How to hide the leading site url from the source code example

http://example.com/wp-content/themes/themename/style.css

Becomes

/wp-content/themes/themename/style.css

Removing the main site URL which http://example.com/ from the source code

I’ve seen many sites running wordpress however they don’t have the Site URL shown in the source code for CSS and JS files.

I know there are many plugins that can help hiding wordpress source code so no one will know it’s wordpress however none of them removes the Site URL from files links.