docs(0-shell: include no-argument option for 'cat' command

Author: heshamalmosawi

subjects/0-shell/README.md

@@ -32,7 +32,7 @@ You must implement the following commands **from scratch**, using system-level R
 - `cd`
 - `ls` (supporting `-l`, `-a`, `-F`)
 - `pwd`
-- `cat`
+- `cat` (including no-argument mode)
 - `cp`
 - `rm` (supporting `-r`)
 - `mv`

subjects/0-shell/audit/README.md

@@ -64,6 +64,12 @@ The use of external binaries or system calls that spawn them is strictly forbidd
 
 ###### Can you confirm that the document `new_doc.txt` is inside the `new_folder2`?
 
+##### Try to run the command `cat` with no arguments.
+
+###### Can you confirm that you can type some text and see it displayed back?
+
+###### Can you confirm that you can stop with `Ctrl+D`?  
+
 ##### Try to run the command `cat new_folder1/new_doc`. Do the same in your computer terminal.
 
 ###### Can you confirm that the output is the same in the project and in your computer terminal?