Very neat. Thanks for sharing - also agree with your sentiment that it feels like content is locked up in Medium, even more so with the subscription plans.
You should probably actually link to the ghost website in your readme somewhere. I was mildly aware and interested in the ghost blogging platform before I saw this, but it might be confusing for people who are not and just googleing "ghost" isn't giving me very helpful results.
That's great, but why just Ghost? Why didn't you create a tool that would just extract your content from Medium and let you use it anywhere else? Now I'm just trapped on Ghost!
Nice. I just looked up Ghost to WordPress (exists) and Medium to WordPress (exists). I like Publii myself for small static sites that even my mom can use, but still like WordPress when I just want to blog.