Make the lib Standard Schema compliant

[c100k]

Problem

No validation lib has been used within libmodulor to keep it "dependency-less". However, the main validation libraries maintainers have introduced a standard :

• https://github.com/standard-schema/standard-schema
• https://standardschema.dev.

Let's comply to it.

Potential Solution(s)

Add the spec to the data type validation layer.