WRF output: display wind vectors on canvas

[dmey]

wrf-python has recently added the capability of extracting Wspd and wdir [as separate 2D variables instead of a single 3D variable; letmaik] and other diagnostic variables from WRF output files (see: NCAR/wrf-python#73). When this feature is added to the next release we should add the option to display wind vectors on canvas. I will assign it to the Future for now.

[letmaik]

Duplicate of #47.

[dmey]

@letmaik this is not a duplicate of #47 as it was specific to using the mesh layer API in QGIS. The purpose of #107 issue is to allow the representation of wind speed and direction only for example as it is described here and which we can implement in the future now that the 2D diagnostics have been implemented in wrf-python. I will reopen this for now