See if cmarkgfm python packaging can replace our build for pelican action

[dave2wave]

In ATR we are using the cmarkgfm python package. We should see if that is suitable for Pelican.

[gstein]

I don't think that existed when I wrote the Pelican work. The default Markdown produced very different renderings between GitHub's "Preview" and how Pelican would render it to our websites. ... So I had to get Pelican to use GFM rather than the default. That was a long time ago. ... If there is an upstream packages to do GFM rendering, then I'm +1 on switching to it.

[gstein]

(deleted comment about the other repo; we moved pelican into here)