cal: Add use case
cal: Add use case

For clarity I changed "-m" to "--monday".
Also, I've removed the "cal -y" for simplicity.
You could just user "cal {year}" to get the same information.
felixonmars/tldr,slash3b/tldr,slash3b/tldr,slash3b/tldr,felixonmars/tldr,felixonmars/tldr