Levels: Simplify for small projects

Currently, the prunix approach for directories is the easiest to apply for smaller, modular projects to my view.

Although there might be a lot to clean up (will add issues), it might be good to have a more "levels" like approach to check from.

e.g. this could be more than enough and all related files will be

Level 1 (according to standard)

.
|-- assets
|-- docs
|-- src
|-- BOM.csv
|-- LICENSE.md
`-- README.md

Level 2: (this is WIP)

.
|-- assets
| |-- export
| |-- media
| `-- README.md
|-- docs
| |-- appendix
| |-- export
| |-- guides
| `-- README.md
|-- src
| |-- electronics
| | |-- export
| |  `-- README.md
| |-- mechanics
| | |-- export
| |  `-- README.md
| `-- README.md
|-- BOM.csv
|-- LICENSE.md
`-- README.md

Note, that at this stage/level 2 I already included the idea for #8 and additionally I think there should be an option to have an export directory under each folder optionally - though I know this is how most software handles it (e.g. KiCAD, FreeCAD, Fritzing).

I will open another issue on that.