[FEATURE] Add support for anvilPy kern

[jgabaut]

With version 2.0.5, an "Unsupported" message was added to handle the experimental feature provided by invil 0.2.8.

Since the current naive awk script doesn't handle multi-line values (which are handled by invil when reading pyproject.toml), an ad-hoc solution would be needed.

[jgabaut]

Version 2.0.9 added some support for anvilPy.

For now, it requires setting anvil.version in stego.lock to 2.1.0.