Draft: Harmonize header levels
Related issue: #4 (closed)
Before:
---
title: "Foo"
...
---
Lorem Ipsum ...
# Title
## Subtitle
After:
---
title: "Foo"
...
---
Lorem Ipsum ...
## Title
### Subtitle
Related issue: #4 (closed)
Before:
---
title: "Foo"
...
---
Lorem Ipsum ...
# Title
## Subtitle
After:
---
title: "Foo"
...
---
Lorem Ipsum ...
## Title
### Subtitle