📄🚀 Add factor labels

[e-lo]

Describe the feature you want and how it meets your needs or solves a problem

As a TIDES user, I want the labels of enumerated values to be documented in the spec so that their descriptions can be self-documenting.

Describe the solution you'd like

New support for this in Frictionless: https://github.com/frictionlessdata/specs/pull/844