Add documentation about development infrastructure

[neumantm]

Resolves #1105

[neumantm]

For me the bullet point list still does not render correctly.
Is that a problem on my side? Or are bullet points not supported in the nalu-wind docs?

[neumantm]

Ok when rendered by readTheDocs, the bullet points are correct (at least with my own rtd project).
(See https://neumantm-nalu-wind--2.org.readthedocs.build/en/2/source/developer/infra.html)

Seems that is either a problem with building the docs outside of rtd or with my local installation.
Could anyone check if they also have that problem?

[marchdf]

@psakievich feels like this should have been merged? It is approved and all.

[psakievich]

I don't recall why it wasn't merged. Found one minor tweak due to infrastructure changes.