## Overview
We use our Saturday library for Markdown rendering, which sacrifices a bit of Markdown functionality in order to support writers who only want to write in plain text, without requiring them to configure anything.
We should also support a Markdown standard like CommonMark, for those who explicitly want it.
## Implementation
In the blog settings page, under **Text Rendering**:
* Enable the "Markdown" option
* Change it to a radio button
* Change the label to "WriteFreely-flavored Markdown"
* Add a new option for the standard we support, e.g. CommonMark
* **Design**: separate this from other options (currently only MathJax).
Update the `collectionattributes` accordingly when the user saves blog settings. Post rendering should check the attribute(s) altered by these settings.