Setup documentation site

[gnidan]

Proposes to address #6

This PR initializes a quick-and-dirty documentation site using Sphinx, with support for:

• Documentation source written in Markdown (CommonMark, sorry)
• Embedded or external JSON-Schemas (draft-04, which hopefully suffices for our purpose)
• Deployment to GitHub Pages (See live: https://ethdebug.github.io/format)

I propose to use Sphinx because it seems to be the only tool to met these criteria:

• Lots of maturity and ecosystem support
• Easy to render JSON-Schemas in whole or in part
• Customizable enough to produce static HTML and/or raw Markdown output (assuming we may want to target an EIP for this work)

Happy to go with another approach if people have better ideas!

[gnidan]

There has been some discussion raised by @cameel regarding rST vs. MD, namely rST does better tables

[cameel]

To clarify: RST has pretty neat support for complex tables, including having multi-line text in cells or merging cells/columns. Table support in markdown is very basic and anything more complex requires including HTML fragments so it becomes less readable and harder to edit in non-rendered form.

But @gnidan mentioned that we can still use directives even in markdown in Sphinx. This might be actually the best of both worlds. At the very least we might be able to include a RST table into a markdown page. These directives might also actually let us make nice tables.

Also, we use Sphinx for Solidity docs and it works just fine for us.