Run output documentationprocess does not export documentation images

[jfy133]

This is related to nf-core/tools#391, and reported for nf-core/eager by @marcel-keller

We could in principle try checking where the paths link to (relative and absolute), and publishDir also the images alongside the md -> html file.

It shouldn't break linting, according to @apeltzer

[apeltzer]

nf-core/viralrecon@c25d62a

This is the fix @jfy133

[apeltzer]

Staging the images to the output_documentation process that generates the rendered report :D

[apeltzer]

Fixed in b2b411b