Docs - Add tips and tricks (or similar) section

**Why are you updating / adding this documentation?**
We should add a tips and tricks section (or set of pages) to highlight common patterns/use-cases like:
- converting pipeline env vars to config
- helm example (env var set in pipeline, before script to read env var and create `$HELM_ROOT/values-files/*.yaml` files)
- terraform example (env var set in pipeline, before script to read env var and create `$TERRAFORM_ROOT/*.auto.tfvars.json` files)
- before script to create the tf state bucket

Will add more examples as I come across them..