Replace sphinx-panels with sphinx-design in docs build
This MR replaces the use of sphinx-panels with that of sphinx-design, as recommended by the sphinx-design github project, following the instructions here.
Maintenance will be performed on git.ligo.org, containers.ligo.org, and docs.ligo.org on Tuesday 30 April 2024 starting at approximately 9am PDT. It is expected to take around twenty minutes and there will be several periods of downtime throughout the maintenance. Please address any comments, concerns, or questions to the helpdesk.
This MR replaces the use of sphinx-panels with that of sphinx-design, as recommended by the sphinx-design github project, following the instructions here.