Climate-categories

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* Remove pygments-csv-lexer dependency for docs building.
* Add function to find leaf children of a category, useful for re-calculating top-level
categories from constituents.

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* regenerate data included in the package to benefit
from latest fixes in data generation scripts.

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* Add updated CRF2013 terminologies for 2021, 2022, and 2023 submission rounds
* The unfccc DI API recently returns unspecified measure IDs.
data_generation/CRFDI_class.py was fixed to ignore them.
* Add CRF2013 terminology for data submitted by AnnexI countries to the UNFCCC
* Drop support for Python 3.7 and 3.8, add support for Python 3.11

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* Change conversion metadata format to use comment chars and a YAML header.

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* Use Python files instead of pickle objects for caching

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* Export Category and HierarchicalCategory types.
* Add ConversionRule.is_restricted attribute to easily check if a rule is restricted to
specific auxiliary categories.