Datasette-render-markdown

* Allow `<a href="...">` attributes, fixes 6

* Improved README.

* Support for Markdown extensions, including GitHub-Flavored Markdown. [Documentation](https://github.com/simonw/datasette-render-markdown/blob/master/README.md#markdown-extensions). 4

* Ability to configure columns in metadata - 1
* Allow customization of wildcard patterns - 3

Added `{{ render_markdown(value) }}` custom template function.

First working release