Add more commands

ls, pwd, cd

Signed-off-by: suosuopuo <suosuopuo@gmail.com>
Using macros to represent sizes

Signed-off-by: suosuopuo <suosuopuo@gmail.com>
Add more commands

mkdir, rm, rmdir, ?, help

Signed-off-by: suosuopuo <suosuopuo@gmail.com>