Language needs to be specified in lubridate (for plot_skill_metrics)

Hi @vagudets,

Together with @nperez we realised that the language in the function lubridate inside plot_skill_metrics.R needs to be specified, otherwise if R is in Spanish it won't read the months properly. I'm using the workstation.

This is what we needed to add (the locale = "en_GB"):

# Get months
  months <- lubridate::month(Subset(data_cube$attrs$Dates,
                                    "syear", indices = 1),
                             label = T, abb = F,locale = "en_GB")

And this is how we played with the languages until we got it right:

I thought it'd be important to take this into account, maybe in some other environments this specification is not needed but it'd be good to add it to the function just in case.

Cheers,

Paloma