Creating a generall css file for rules applied to all pages

[xa31er]

This will help with adding new pages, and also untangle the codebase.

We could also create different files for commonly used page sections, like headers, footers, sidebars, search bars...

[pihedron]

This will be solved by #138 soon. Please check it out.

[Naviary2]

In the meantime, the PR is not ready.

[Naviary2]

This has been partially solved by #285 by adding a header component! What remains is other items inside each page's stylesheet that are in common across the other pages.

[xa31er]

Yes, I think that can be done pretty quick.

[Naviary2]

We can use this skeleton css sheet to deduce most of the similarities between stylesheets across the whole website
https://github.com/Infinite-Chess/infinitechess.org/blob/main/dev-utils%2FSKELETON.css