* first pass at the single gpu doc * overview: improved clarity and navigation * WIP * updated intro and deepspeed sections * improved torch.compile section * more improvements * minor improvements * make style * Apply suggestions from code review Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com> * feedback addressed * mdx -> md * link fix * feedback addressed --------- Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>