Conversion to/from normalized RGB

[MisterRedsun]

Currently, conversion to and from 0-255 range RGB is supported in this extension, but I find that I often have to convert back and forth between 0-255 range and 0-1 range RGB. Adding a conversion target for normalized RGB would keep me from having to manually divide each color by 255 each time I make a slight color modification.

[jiripolasek]

@MisterRedsun

What about this:

[MisterRedsun]

That's perfect!