[guide] use ARC with galaxy

[Brilator]

We could need a guide to show how to

• load your (private) ARC into Galaxy
• [run a workflow there] -> reference to Galaxy guides
• write the workflow and results back to the ARC

[Brilator]

For private ARCs

• on DataHUB side: create PAT with read_api / api
• on Galaxy side: "User" -> "Preferences" -> "Manage Information" -> "API Read Access Token"

[Brilator]

Export to ARC:
"Export datasets to remote files source" -> "DataPLANT DataHUB ARCs" -> select ARC -> "Choose your datasets"