to write output, you would usually just use the print builtin
since commanders are just lua custom commands but this does not
consider the fact of pipes or other shell operators being used
to redirect or whatever.
this adds readable/writable "sinks" which is a type for input
or output and is currently only used for commanders but can be
used for other hilbish things in the future
prelude is no longer. it is now nature.
organized the single file prelude into multiple
source files and renamed it to nature. this is coming
after thought that it can turn into a general hilbish
lua core, with user facing modules as well.
this introduces the `nature.dirs` module, to interact
and get recently changed to directories and last/old
cwd.