Add a unifying generic theme to the site

[yu-nix]

Adjust the global SCSS to have some font typefaces and general colorations like background color and text color.

Integrate SCSS variables into modular SCSS so that they are actually used as they should be. (Headers, subheaders, subtext, paragraph text, those sorts of numbers).

The end product should be a site that looks uniform, unlike what it is now. It should be plain so that it's easy to add on to it and modify it.