Ensure `M` enables metric
Ensure `M` enables metric

It seems reasonable, per the documentation (under the section, "Weather Units"), that `?M` would enable metric ("metric (SI), but show wind speed in m/s") all by itself.

> By default the USCS units are used for the queries from the USA and the metric system for the rest of the world. You can override this behavior...
> ...
> `curl wttr.in/Amsterdam?M`  # metric (SI), but show wind speed in m/s

In the USA, we have to pass `?m&M` (`https://wttr.in/?m&M`) to get metric and meters/second. If we just pass `?M`, we get USCS units for everything else and windspeed in meters/second.
chubin/wttr.in,chubin/wttr.in,chubin/wttr.in,chubin/wttr.in