Add spec-compliance-matrix in opentelemetry-specification.

[fractalwrench]

Originally raised in the old repository: embrace-io/opentelemetry-kotlin#489

Summary

Since OpenTelemetry Kotlin has become an official SDK, I would like to add kotlin.yaml to the spec-compliance-matrix directory in the opentelemetry-specification.

Motivation

At the moment, there is no compliance matrix for Kotlin. As a result, it is difficult to clearly understand:

• which parts of the specification are already implemented,
• which parts are missing or incomplete, and
• where new contributors can meaningfully participate.

By adding a Kotlin matrix, potential contributors will be able to quickly identify gaps and propose improvements more easily.

I understand it should be done after opentelemetry-kotlin org would be moved.
Then, it is just an idea.

Note

I understand this should only happen after the repository is moved from embrace-io to open-telemetry, so this issue is meant as an early proposal for discussion.

[fractalwrench]

I've started this effort here: open-telemetry/opentelemetry-specification#4833