[docs] specification of custom model

[mirkoCrobu]

Motivation

Create a model specification (like the app specification) for the custom model

Change description

add custom model specification file

Additional Notes

Reviewer checklist

• PR addresses a single concern.
• PR title and description are properly filled.
• Changes will be merged in main.
• Changes are covered by tests.
• Logging is meaningful in case of troubleshooting.

[CLAassistant]

All committers have signed the CLA.

[giulio93]

Why we say that a AI Brick manages a specific AI domain, if we can have a N:N relationship and even swap between models that should be relagated to one Domain.
E.I. How is possible that Object detection can be used by Face Detection?
Is this restriction on AI domain just a definition but not an hard contraint in the real application?

[mirkoCrobu]

it is a bit confusing. Do you think it is clearer the following:

Model Versatility: A single AI Model can be compatible with multiple Bricks. Compatibility is determined by the model's category. For example, a model belonging to the "Object Detection" category is automatically compatible with both arduino:object_detection and arduino:video_object_detection bricks.

[giulio93]

I think the document is not general enough, everything seams to be tight around the EI model structure, we might need another iteration

[dido18]

I would make the following changes:

• Remove the numbers in the titles/subtitles.
• start with the "AI Arduino specification"
• make the AI brick discussion a "note" of the document.