Add documentation for Dragon launcher

[al-rigazzi]

Description

The Dragon launcher needs to be documented.

Justification

The Dragon launcher needs to be added to existing documentation about how to start Experiments in SmartSim. In particular, a tab group for the Dragon launcher, i.e. for Experiment(..., launcher='dragon'), must be added to existing documentation pages.

Implementation Strategy

The ticket can be summarized as two acceptance criteria:

• [ ] Bring all docstrings up to SmartSim's highest standards
• [ ] Make sure users can see from the docs that launcher='dragon' is an option when starting an Experiment