Build the NEML2 documentation along with MOOSE docs

[dschwen]

Motivation

We're starting to add NEML2 objects hosted in MOOSE based apps. We need those to be documented, and their documentation to be built. NEML2 now has a self-documentation feature similar to MOOSE.

Design

We should trigger the NEML2 documentation build and upload in Civet and there should be a link (maybe in the NEML2 action documentation) to those documentation pages.

@hugary1995 @loganharbour

Impact

Improved documentation.

[hugary1995]

There should be no technical difficulty as neml2 docs are also just static pages. This will however bring in additional dependencies. We currently use doxygen, doxygen-awesome, as well as a few other python packages. I think the moose build env already has most of these dependencies, with doxygen-awesome being an exception.

[dschwen]

@VanDavv, it would be great if you didn't link this issue from a dozen unrelated repos...

[VanDavv]

I'm really sorry, I was not aware that it would cause a mess like this, didn't want this guy to infect anyone and didn't want to sound like a bot myself, hence the evidence 😔
As soon as I realized that it's causing a mess, I stopped adding any links and now I'm moving back hiding my comment as GitHub took action already

[loganharbour]

Need anything from me on this?

[hugary1995]

We don't have a set plan for this. I see two paths forward, so I need to discuss this more with Daniel. Regardless how we want to proceed, I'll make sure to involve you in our conversations early enough so that I don't create another CI mess.

[loganharbour]

so that I don't create another CI mess

Hah. Much appreciated