Editor for different project types

[nighca]

Reusable components:

• Code editor, Code editor for different class frameworks #2803
• History
• Load/export & persistence solution

Routing / page structure note:

• Supporting multiple project types may mean providing dedicated editor pages per type (not necessarily a single unified editor page that switches by type).
• Route-level work (how editor entry URLs map to a specific type/editor implementation) should be captured here, while project detail/community route-level work lives in Project page for different project types #2805/Other community pages #2807.