Create directory structure

There is no right or wrong structure at this point. We can always adapt as needed.
```
vdm/
├── spec/ # Specification files only
│ ├── foundations/ # Core spec foundations
│ │ ├── directives.graphql # GraphQL directives
│ │ ├── units.graphql # Unit definitions
│ │ ├── scalars.graphql # Scalar types
│ │ └── common.graphql # Common types and patterns
│ ├── domains/ # Domain-specific specifications
│ └── queries/ # Query definitions and schema
├── docs/ # Documentation and resources
│ ├── examples/ # Example specifications
│ ├── templates/ # Reusable spec templates
│ ├── user-guides/ # User documentation
|── resources/
│ └── vss-migrated/ # VSS migration resources
```