Add params UGUST and VGUST for productnum 8 (accum)

[MennoTammens]

KNMI HARMONIE has wind gusts as U-gust and V-gust, as maximum value over the previous hour.
After conversion to GRIB2 these are parameters 23 and 24, in paramcat 2 (TABLE 4.2-0-2), with pdtnum 8.

[MennoTammens]

Example: https://example-grib.s3-eu-west-1.amazonaws.com/harmonie-gusts-test.grib2

[norulz]

Thanks @MennoTammens
Getting XyGrib moving again. Good to have you around :-)