I very often find myself using or suggesting this project layout, so I've gone ahead and cookie-cuttered it so everyone else can use it too!
Its as easy as
cookiecutter https://github.com/KenwoodFox/Project-Template
If you dont have cookie-cutter, install it from here!
.
└── YourProject
├── CAD # CAD Files, 3D objects (cases, brackets, big things)
├── Docs # Documentation (setup by default with Sphinx)
├── Firmware # Firmware (setup by default with PIO)
│ ├── include # Include files like pindefs and headers
│ ├── lib # Custom lib files like project objects and memory
│ ├── src # Source code files
│ └── test # PIO Tests
├── Hardware # Hardware (setup by default with KiCAD and KiBOT)
│ └── YourProject # KiCAD project with the same name
│ ├── Libraries # External KiCAD libs!
│ └── Stencils # Stencils and jigs
└── Static # Pictures and Docs