feat(wind): Bias correct wind speeds based on scaling to a known average (alternative)

[coroa]

Alternative to #403 .

Adds a new function :py:func:atlite.datasets.era5.retrieve_average_windspeed
to retrieve average windspeeds. This dataset function is called by
:py:func:atlite.wind.calculate_windspeed_bias_correction to derive a bias
correction which can be passed to the default wind generation.

Example usage:

windspeed_bias_correction = atlite.wind.calculate_windspeed_bias_correction(
    cutout,
    real_average="gwa3_250_windspeed_100m.tif",
    height=100,
)
cutout.wind(
    atlite.windturbines.Enercon_E101_3000kW,
    windspeed_bias_correction=windspeed_bias_correction,
    windspeed_height=100,
)

Closes #373 .

Changes proposed in this Pull Request

Checklist

• Code changes are sufficiently documented; i.e. new functions contain docstrings and further explanations may be given in doc.
• Unit tests for new features were added (if applicable).
• Newly introduced dependencies are added to environment.yaml, environment_docs.yaml and setup.py (if applicable).
• A note for the release notes doc/release_notes.rst of the upcoming release is included.
• I consent to the release of this PR's code under the MIT license.