CSS will not work on HTML page

I have a github repositoryhere that I am trying to deploy onto this URL but everytime I go onto the page the CSS doesn’t work. When I go back to my local files, the CSS seems to be working properly, but on Git the CSS does not load. I am not sure what exactly the problem is here

You have this path to your css

<link rel="stylesheet" href="css/style.css">

but in your repository you don’t have a css directory, you only have the style.css in the same level as your index.html

I’m not sure I quite understand. How do I add the CSS directory to my repository?