Project Structure Docs

**Did you find any pain points?.**

The Project structure docs only talk about the "bare minimum" required to make a project work, but it doesn't talk about enforced project structures and supported scenarios when configuring some of the perla features.

We should add better information related to why we want this project structure and what are the limitations perla has with non-standard (for perla) project structures

**Did you find something cool about it?**
N/A

**Any other thoughts?**
N/A

Taken from #96

Start by locating the existing Project structure documentation and reviewing issue #96 for related context. Explain why the structure is expected and which Perla features or scenarios are limited by non-standard layouts; done means supported and unsupported structures are clearly documented.

Written by the indexing model from the issue text.