Manage the life cycle of your exported functions with shared
conventions, documentation badges, and non-invasive deprecation
warnings. The 'lifecycle' package defines four development stages
(experimental, maturing, stable, and questioning) and three deprecation
stages (soft-deprecated, deprecated, and defunct). It makes it easy
to insert badges corresponding to these stages in your documentation.
Usage of deprecated functions are signalled with increasing levels
of non-invasive verbosity.
