IAMconsortium/nomenclature: Release v0.2

Highlights A detailed documentation is now available under nomenclature-iamc.readthedocs.io. The new process function makes interaction with the nomenclature package more seamless. (link to the docs). Variable region aggregation can now be combined with renaming. (link to the docs) Tag code lists no longer use the format but employ "f-strings" in closer alignment with python. (link to the docs) The RegionProcessor.apply() function now has better performance