Add page on wind speed data, specifically height

[williamhobbs]

See pvlib/pvlib-python#1814 and https://forum.pvsyst.com/topic/3377-height-of-wind-speed-data-used-to-derive-pvsyst-thermal-parameters/. Apparently PSM3 uses MERRA2 2m wind speed, but PSM2 used 10 m wind speed. It seems that most modeling software assumes input wind speed is measured at 10 m, so clarifying this would be helpful.

Additionally, it could be interesting to pull some MERRA2 data, compare to NSRDB PSM3, and confirm that it matches.