[Feature] A very simple "how to use template-builder" tutorial

**Is your feature request related to a problem? Please describe.**
Following #465, we make template building tooling accessible to people with some initial Python and template-building expertise and sufficient motivation.

**Describe the solution you'd like**
We'd also like to have a simpler tutorial in the diataxis sense, that can run locally with provided small example data, for more casually interested parties trying to gauge whether they could make a template or not.