With#3637 merged (fixed#2340), we now have an environment variable:CODER=true that's available in all Coder workspaces.

We should document that this variable is available, and can be used for e.g. dotfiles customization.

if [[$CODER==true ]];then# Inside a Coder workspace.    custom_coder_logicfi

We may potentially want to expand the number of env variables we have and are documented, see#2340 for a discussion about potential variables to add.

For reference, here's how Codespaces document theirs:Default environment variables for your codespace

Definition of done

The user can read Coder docs and find out about useful environment variables inside workspaces.