It seems the behaviour of the default opener (xdg-open) varies across platforms
and environments. Details are documented in the issue. To prevent an empty file
from being accidentally opened leading to unexpected behaviour, we are adding a
guard with the message that the empty file should be opened using edit or open
option.

Update README.md -Milis

Milis Linux support

Milis Linux support

Fix a broken link

Document how to install fish quitcd function

It was not clear that the name of the file should match
the name of the function.

Readme changes

E.g. BSD curses.

- Add BSD
 - Raspberry Pi is not an OS
 - Non-exhaustive