Specify in project description that it supports multiple Unices

[mmcco]

This is trivial, but the this project's GitHub description says:

Fetches system/theme information in terminal for Linux desktop screenshots.

I'd hate for someone to get turned away without realizing that screenFetch supports other Unix-like OS's (e.g. FreeBSD), so replacing "Linux" with "Unix" may be worthwhile.

Thanks for your time, Mike

[darealshinji]

@KittyKatt can you change the description? Maybe a term like "Unix-like environments" should be used, as it can be used on Windows too (Cygwin, Msys2, Ubuntu on Windows), which isn't a Unix-like OS.