Add markdown table support for Read the Docs

[zstadler]

By default, Read the Doc's Sphinx engine does not support Markdown tables.

As a result, here we see

rather than

github.com/ryanfox/sphinx-markdown-tables provides an extension that adds the required support. According to its docs, the solution is to add sphinx_markdown_tables to extensions in conf.py, like so:

extensions = [
    'sphinx_markdown_tables',
]

Note:
According to this issue, you may also need to add sphinx_markdown_tables to ReadtheDocs' requirements.txt file.

[Gregor Sturm]

Hi @zstadler,

thanks for the hint, that looks great!
I currently don't have a lot of time to maintain this package -- do you want to put a PR together?

Cheers,
Gregor