Add explanation of SHM config command

[JimMadge]

✅ Checklist

• I have searched open and closed issues for duplicates
• This is a request for a change to documentation
• This isn't a feature request or bug report
• This isn't an open-ended question (open a discussion if it is).

📒 Where is the problem?

The SHM deployment guide doesn't explain that you can see the configuration of a previously deployed SHM.

This could be very useful if users need to update/redeploy/validate an existing SHM.

📝 Required documentation changes

Add a hint box explaining dsh config show-shm can be used to see the configuration of your selected context's SHM.