Add docs downloads

[skasberger]

Add docs as downloads (pdf, html, epub).

Prepare

• [ ] Define, where to place them inside the documentation

Implementation

• [ ] Update Docs
• [ ] Run tox

Review

• [ ] Docs

Follow-Ups

[pdurbin]

As discussed during the 2024-02-14 meeting of the pyDataverse working group, we are closing old milestones in favor of a new project board at https://github.com/orgs/gdcc/projects/1 and removing issues (like this one) from those old milestones. Please feel free to join the working group! You can find us at https://py.gdcc.io and https://dataverse.zulipchat.com/#narrow/stream/377090-python