Enhance theme to allow switching skins client-side

[ashmaroli]

Key points

• Generate a complete CSS file for each skin:
  • assets/css/style.css (default stylesheet / classic skin)
  • assets/css/dark.css (dark skin)
  • assets/css/solarized.css (solarized skin)
  • assets/css/solarized-dark.css (solarized-dark skin)
• Use javascript to render a <select/> element in the site-footer to allow switching stylesheets on a deployed site.
• Introduce custom-scripts.html placeholder to allow adding more scripts before the closing </body> tag.

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Live Demo: https://ashmaroli.github.io/minima/

[mattr-]

I like this idea. What do you think about moving the skin switching bits to a documentation example? This will give folks an example that they can use to seamlessly implement something for their own site and allows us to avoid implementing color scheme switching functionality directly to the theme.