The old dark mode is dropped and replaced with nord. Light and black
themes were also rebased on the Nord theme.
Code blocks now appear the same way my terminal windows appear in my
Linux configuration, emulating a side titlebar.
This commit adds the Nord theme into the list of available themes. The
Nord theme is now the default theme for dark-based systems.
Theme buttons now have their own class to make it easier to change
them without too much work.
The `style.scss' file has been split up in three different files:
- main.scss, the new file to load from the HTML page, imports the two
other files
- themes.scss, containing all the theming of the websites
- style.scss, containing the rest
All websites loading the theme will now need to load it from
`main.scss' instead of `style.scss', likewise with the `.css'
extension
