Add new templating overview docs

Zebedee Nichollsrequested to merge
new-architecture-docs into main

Description

Sets out the direction I think we should go in with our templating stuff.

A first cut is in https://gitlab.com/magicc/fgen/-/tree/template-clean-up-sketch?ref_type=heads, but it's super hard to understand. I'll make other PRs which split out the steps.

Checklist

Please confirm that this pull request has done the following:

- [ ] Tests added

  • Documentation added (where applicable)
  • Changelog item added to changelog/
Edited by Zebedee Nicholls

Merge request reports