Unify w/ pydata sphinx theme

[jarrodmillman]

• color schemes
• variable names
• config files

[alphapapa]

As explained in our meeting the other day, we can more easily make changes in this project than in pydata-sphinx-theme, so we'll generally try to follow its example.

Doing this well will require some familiarity with both projects, so I'll treat this as a longer-term project and dig into it as I learn about them.

[alphapapa]

In our meeting now, here's the basic plan we've got:

1. Add Sass to our build process.

• Already supported by Hugo, in fact: https://gohugo.io/hugo-pipes/transpile-sass-to-css/
• And already used by us here:

  scientific-python-hugo-theme/layouts/partials/css.html

  Line 26 in bd2f44d

  {{ $css := resources.Get . | toCSS $cssOpts -}}

3. Add Makefile rule to take Sass from the pydata-sphinx-module repository, copy the files into our project, build them into CSS, and place them in the right place to be served as part of our theme.
4. Begin editing our HTML/CSS to use the parts from the pydata-sphinx-theme (e.g. editing our CSS classes, using their variable names, etc).

[alphapapa]

Ok, as a first step, I've pushed 03d2d9c which adds a rule to the Makefile to pull the SCSS files from the pydata-sphinx-theme repo and add imports for them to a single all.scss file. Next is to have that file built into a CSS file by Hugo and served with the site. I'll work on that tomorrow.

@jarrodmillman @brianhawthorne

[alphapapa]

Closing in favor of new meta-issue: #302