Feature set - documentation

[PeterMortensen]

Maybe it is implicit from the 1994 standard and "CORE", but I suggest making it explicit in the ReadMe file if the floating point word set is supported or not (or if there is some other kind of floating point operations possible).

It could be in the form of a feature list (if it is not too short), included what is not supported.

The feature list could also include some indication of operating system(s) this Forth runs on (e.g., is it only Linux?) - I don't assume it is a bare-metal Forth.