Document User Quotas

[wildintellect]

VEDA instances now use a fixed size EBS volume instead of EFS. Each user now has an enforced quota.
At initial outset this is:

• 100 GB each for VEDA
• 100 GB each for MAAP
• 50 GB each for GHG

However this is undocumented, and there are little to no tools to help users manage this storage.
du is a terminal tool to at least help people get started, see also https://github.com/nachoparker/dutree (which we may want to include by default).

In order to user du well we need to link to good docs, and note things like shared directories to exclude from calculation. For most users that means:
du -ch --max-depth=1 --exclude=shared

Acceptance Criteria

• PR updating VEDA Docs
• PR updating GHG Docs
• draft branch on MAAP Docs with need MAAP Hub information