feature: docs as tests - validate computed output against the output in the codeblock

[benjamincburns]

Problem

I want to know if I've introduced a bug in my project that broke my documentation.

Describe the solution you'd like

There could be two parts to this.

• make pycon work more like docstring tests, and error if the computed output doesn't match the output shown in the markdown
  • Ideally this solution would be easy to replicate for typescript/javascript once TypeScript support (draft) #70 merges
• add an option that makes other codeblocks work more like traditional replay tests by capturing the output to files somewhere, and then on recompute, checking the recomputed outputs against those files

[pawamoy]

Thanks for the feature request @benjamincburns 🙂 As you noticed in #71, there's a relevant discussion in #4. To allow keeping the whole context in the same place, lets continue the discussion there (but I'll keep this issue open as it's more narrowly-scoped).