Document working modes

[n8willis]

I think it would help users a lot to document which capture modes do and don't work (well, probably it's simpler to just track the "dont"s, since those are somewhat more like bugs). Right now the README just says "some".

[derrod]

That note is mainly relevant to the Windows driver which exposes a lot more (v210, v410, bgr5, etc.) whereas the Linux driver only has a YUV 422 and RGB24 mode. The latter unfortunately doesn't work.