Update newgrp(1) to include examples.

[felix.the.red_gmail.com]

Summary

Add examples provided by Mark Saad.

Test Plan

PR: 167742

[maxim]

usr.bin/newgrp/newgrp.1

72–79

You probably want to use # as a root shell prompt and $ for non-root. Another option is to remove the prompt completely.

[ziaee]

usr.bin/newgrp/newgrp.1

71–80

It would need to look something like this, but I think this probably shouldn't go here, and should instead be an example in pw(8).

72–79

Using prompts in examples is highly undesirable because of copy paste.

If using prompt, using % for user shell prompt is fine, bsd traditional, but # must be used to represent root shell prompt.

[felix.the.red_gmail.com]

• Remove shell prompts from examples in newgrp(1).