Is there any online service that offers a WYSIWYG markdown editor (something like Notion or Ghost Blogging Editor) that links directly to Github?

My use case is: I use Middleman (or Jekyll) to setup a simple CMS for an online guidebook that we're launching. I like both the developer-friendliness and flexibility of Jekyll/Middleman, at the same time I need to expose a user-friendly interface for the Content team to update/write.

Right now I can only see 2 options:

1. Use Middleman/Jekyll - Pro: easy for dev to customize structure - Con: difficult for non-technical editor to update

2. Use - Pro: easy for editors to update content - Con: difficult for dev to customize CSS and data structure