ci: document of uv tool usage

Signed-off-by: Davide Madrisan <[email protected]>

README.md

@@ -23,6 +23,10 @@ HadCRUT5 data are downloaded from: https://www.metoffice.gov.uk/hadobs/hadcrut5/
 The following plots have been generated by the Python scripts `hadcrut5-plot.py` and `hadcrut5-bars.py`.
 They require the Python libraries: Matplotlib, netCDF4, NumPy, and Requests.
 
+If Python and the required libraries are not installed on your system, you can simply
+[install](https://docs.astral.sh/uv/getting-started/installation/) `uv` and run the commands listed below prefixed
+with `uv run`. For example `uv run ./hadcrut5-plot.py`.
+
 ## hadcrut5-plot.py — Script usage
 
 ```