Add basic ls implementation

[Sigmanificient]

Based on my ls school project source, I recreated a small ls utility that features the following flags:

• a: do not ignore entries starting with .
• l: use a long listing format
• R: list subdirectories recursively
• d: list directories themselves, not their contents
• r: reverse order while sorting
• t: sort by time, newest first

[proh14]

Add the macros for the command info. checkout echo for details on this
use strerror instead of a switch for errno.
preferably do not use __attribute__((nonnull)) and does kind of stuff
Add copyright notice to manpage
format the code with clang-format if not formated.
thx ;)

[proh14]

all good :D thx