Improve Copy+Paste from ChatGPT

[bombino]

We do a lot of copying and pasting from ChatGPT, and it has some bugs.

The worst ones are:

• it will insert the language name and an "Edit" link into pastes of Code blocks.
• Headers are bolded in addition to being a header, making fonts strange looking (in fact, I would support always removing Bold from headline blocks)
• Headlines strangely map in in terms of size. Can we make ChatGPT's h1 the equivalent of GitBook's h1?