readthedocs URL change

[chapman39]

• renamed readthedocs URL to llnlsmith. Open to other suggestions

old links (still preserved):

• https://app.readthedocs.org/dashboard/serac
• http://serac.readthedocs.io/en/latest/

new links:

• docs settings page https://app.readthedocs.org/dashboard/llnlsmith
• user-facing docs page https://llnlsmith.readthedocs.io/en/latest/

various external prs renaming docs and other things:

• Rename Serac to Smith radiuss-spack-configs#156
• Rename Serac to Smith uberenv#153
• Rename Serac to Smith blt#747
• Rename Serac to Smith Tribol#184
• Rename Serac to Smith mfem/mfem#5160

[tupek2]

You know, our primary purpose has evolved a bit. This is all certainly true, but a big focus is also now on "differentiable multi-mechanics." Brandon should weight in, but I'm going to suggest:

Its primary purpose is to investigate multi-mechanics abstractions and solver strategies on emerging computing architectures, as well abstractions for differentiable multi-mechanics for both static and dynamic applications.

[tupek2]

I'd suggest merge as is, but a future thing might be to make some of the wording here more up to date with the current focuses. (its not wrong, just missing some emphasis)

[btalamini]

I agree that the wording is stale. This is true for a lot of the docs at this point. Let's get the new site up and running and tacklie doc improvement in our goals for this year.

[chapman39]

created an issue #1508

[btalamini]

Thanks for getting the new site goign!