sync manpage and help info

Signed-off-by: Leonardo Hernández Hernández <leohdz172@protonmail.com>

add `-v` flag to the manpage

Thanks @Humm42

Merge pull request #180 from Humm42/manpage

add dwl(1)

add dwl(1)

Documentation is good.  Man pages are documentation.  A program without
a man page is worthless.