add notebook yaml highlighting

[Yelinz]

makes the yaml nicer to look at

[simoninithomas]

Hi there, thanks for your contribution, though, there's a problem with the PR because it created a lot of metadata, so for now I can't merge it.

[Yelinz]

Ok, should I try to reduce it to minimal changes?

[simoninithomas]

Hi if you can please yes, the easiest is to take the initial notebook and modify from there directly

[Yelinz]

Redid the changes with text editor to avoid touching the metadata. Now only the 2 lines where needed are changed.