Support TAF variable wind direction

[cquinlan-cirium]

Description

I've added support for variable wind direction as it is possible for a TAF string to contain this information as seen below: MNPC 301530Z 3018/3118 16006KT 100V200 5000 RA/TSRA FEW014CB BKN016TCU BECMG 3100/3102 VRB04KT 6000 -RA/HZ BKN016

Checklist

• [X] Tests covering the new functionality have been added
• [X] Documentation has been updated OR the change is too minor to be documented
• [X] Changes are listed in the CHANGELOG.md OR changes are insignificant

[devdupont]

Looks good to me. Thanks for such a thorough PR!