New Open Data notebooks

[alinalerneral]

Description

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

[milanavuckovic]

• Most of the aifs_ens-medium* notebooks have a broken link that I introduced at some point when we added AIFS. The broken link is in the fourth cell (https://confluence.ecmwf.int/display/DAC/ECMWF+open+data%3A+real-time+forecasts+from+IFS+and+AIFS+from+IFS+and+AIFS). Second +from+IFS+and+AIFS should be removed from all the notebooks that have it
• Notebooks with ensemble spread downloaded (not calculated) that have *1.0 for spread, should instead have grib_scaling_of_retrieved_fields="off" parameter added to the mcont function. A sentence in the cell above it could be added to explain this. Something like 'Metview automatically transforms units of some parameters including temperature from Kelvins to Celsius, however for ensemble spread we don't want this scaling, so we turn it off by setting grib_scaling_of_retrieved_fields parameter to off in the mcont function' or something similar.
• notebook that plots clouds is not included on charts and is too different, so we'll not include the aifs either until we have it in earthkit or produce with Metview
• notebook aifs_ens_medium-100ws-mean-spread.ipynb has 10m instead of 100m in the link to the product so it links to the wrong chart. Add a zero.
• Feel free to fix typos if you spot them.