Add example for command n,g,p and grid, update date now examples (#4622)

docs/commands/p.md

@@ -9,3 +9,15 @@ Switch to the previous shell.
 ## Signature
 
 ```> p ```
+
+## Examples
+
+Make two directories and enter new shells for them, use `p` to jump to the previous shell
+```shell
+> mkdir foo bar; enter foo; enter ../bar; p
+```
+
+Run `p` several times and note the changes of current directory
+```shell
+> p
+```