Support for notebook 5.0 markdown cell attachments

[parente]

Notebook 5 supports attachments in markdown cells. nbviewer should probably support the same. Just opening this as a placeholder. I haven't looked much into what's involved yet. (Will updating the notebook components used in nbviewer fix it? Adding post_embedhtml.EmbedPostProcessor to what nbviewer is running (jupyter/nbconvert#328)?)

[scottdraves]

any plans to address this?

[carlthome]

ETA?

[rmadar]

I also think this feature would be very good to have, in order to fully exploit notebook exportation into different formats (typically useful for slides).

[scottdraves]

We would like to develop a fix for this. Any special guidance from the maintainers?

[rmadar]

I am neither a developer nor a maintainer but I had started to look at the code and I think it might come from line 40 of nbconvert/preprocessors/convertfigures.py where only outputs cells are looked at (while copy-pasted figures are stored as attachments). Maybe that can help ...

[turkialjrees]

Inspecting the HTML file, it's easy to spot the problematic piece of code, as what in the notebook was

becomes
<img src="./graphics/githubSF.png" alt="test" width=600>.
To give a bit more context with images, the notebook cell