Push aligned sequences up to data.nextstrain.org for download availability

[emmahodcroft]

Context

We currently provide links to download the curated sequences & metadata, which is great. However, many times one just wants to start with an aligned sequence set (particularly in cases when alignment can be tricky, as with MPX). We generate this as part of our workflow, it would be great to:

• Add a rule that uploads aligned.fasta to data.nextstrain.org (either after alignment or at the end)
• Include a link to this aligned file in the description at the bottom of builds (and in the github repo)