[HowTo] Update the docs

You can generate the docs via cake doc:site or cake doc:site:watch.

A convenient workflow is to run cake doc:site:watch, and then, from another tab, run sudo http-server -p 80 from the docs folder (/docs/). (You may need to install http-server if you don’t yet have it: npm install --global http-server.) Then go to http://localhost in a browser.