Add clearer formatting for long headers

[Mika Vilpas]

https://sakura-paris.org/dict/#/dict/%E5%A4%A7%E8%BE%9E%E6%9E%97/prefix/%E5%B9%B4%E8%80%81%E3%81%84%E3%82%8B/0

When reading this, I'd like to focus on understanding the definition itself, not so much the header.
It's useful but it looks too much like the content and it's confusing.