[Docs]: Pixi context + GCP project guidance for LBL org users

[mglbleta]

Location of the issue

etl_merge/my_etl_project/README.md

Suggested fix or improvement

• Pixi context (why pixi, when pixi)
• GCP use explanation (go to old repo to find previous edits)
• GCP project guidance for LBL org users (ask for BioCirV permission)