Ismn

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- Fix bug where station names in metadata can be different between Header and CEOP format.
- Custom Sensor Metadata reader now also checks the measured variable.

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- Added functionality to provide fill values with predefined custom metadata readers.
- Documentation and constants updated.
- ``ISMN_Interface.read_ts`` raised an error when np.int64 was passed.
- Fixed for `pygeogrids>=0.4.2` where dist=np.inf can be returned if

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- Add module to assign custom metadata readers to ISMN_Interface
- Notebook added that describes using a custom metadata reader
- RTD build uses a separate, smaller environment.yml now (and mamba)
- ISMN_Interface now has a method to create an instance of itself for a selection of (`ISMN_Interface.subset_from_ids`)

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- Citation for `COSMOS-UK` network added
- Metadata for empty variables now also generated
- Added citation for `SMN-SDR` network (`Issue 44 <https://github.com/TUW-GEO/ismn/issues/44>`_)
- Update station plots with keyword argument for font size

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- Fixed bug in the metadata dataframe when not using all available networks.
- Citation export functions added to `Collection` and `Network` components.
- Citations for all networks are now stored in this package until they are reliably provided together with the data
- It is now possible to pass multiple allowed variables when filtering sensors.

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- Remove setuptools_scm from dependencies
- Remove option to pip install ismn[plot] for now.