Add vWii info to wii-loaders.md

[mpgiii]

Description USB loaders page didn't have links to vWii, and also linked to forwarders that do not work on the vWii -- this pull request adds that info.

[mpgiii]

It may be worth adding info about converting Wii forwarders for vWii, but I couldn't be assed to actually write up that info

[playerjmr]

hold off on this, I might cook something up

also the Wiiflow forwarder works on both Wii and vWii already

[mpgiii]

Hell yeah sounds good. Thanks -- will leave the pull request open for now until you're done metaphorically cooking. Also, neat that the WiiFlow forwarder supports vWii.