Ivalo color theme

This theme is entirely based on Nord color palette (https://www.nordtheme.com), but with darker background and improved legibility with a few warmer notes.

These improvements were made because I felt the original Nord theme was, although very elegant, lacking in contrast.

I'm a front-end developper, so the changes made are mostly directed at Javascript and JSX writing.

Thanks to https://github.com/arcticicestudio for the awesome work that served as a base for Ivalo.