fs: shell: add cat file command
fs: shell: add cat file command

Add cat command to fs shell module.
This command prints to the standard output
the given files.

Signed-off-by: Shlomi Vaknin <54c0a9b681c5459019f43c3dc65e0278ef9673d9@gmail.com>

finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr