New starter submission

[ArnaudLigny]

👋 Hi, I'd like to submit a new theme successfully tested on Forestry:

name: The butler
preview: https://demo.cecil.app/
image: https://raw.githubusercontent.com/Cecilapp/starter-blog/master/static/images/cecil-preview.png
author: Arnaud Ligny
  versions:
  - name: Cecil
    repo: https://github.com/Cecilapp/starter-blog
    branch: master
  textline: A ready to use static blog, powered by Cecil and Hyde.

Submission checklist

Make sure to setup up things in Forestry:

• [x] Import is complete
• [x] Sidebar sections are visible
• [x] Media upload folder and public path are defined
• [x] Instant Previews are working