Update site layout to v7

[hnarayanan]

Here are some guiding principles for the new design:

• Use simpler, modern CSS (grid, variables etc.) and remove usage of frameworks
• Make the HTML layout more semantic
• Allow for a more playful grid
• Allow for per-page art-direction
• Highlight new patronage system for explanatory writing

[hnarayanan]

Inspiration

• https://distill.pub/2018/building-blocks/
• https://trentwalton.com/2013/08/12/human-interest/
• http://tobiasahlin.com/