Improve overall depth and presentation

[ehenoma]

We should improve the style guide by:

Generally updating rules

New rules have come up and existing rules may have slightly changed over the past two years.
We should address that in an updated guide.

Making it more structured

Using a website instead of document can make the style guide more discoverable and navigable.
It also allows us to go more in-depth about specific rules and provide some interactive features
like comments.

Adding more topics

There are many topics left out right now. We should cover all the subjects that would come up
in a general code review.