Add dunstify manpage

Author: bynect

test/test-install.sh

@@ -38,6 +38,7 @@ testprefix/share/fish/vendor_completions.d/dunstctl.fish
 testprefix/share/fish/vendor_completions.d/dunstify.fish
 testprefix/share/man/man1/dunst.1
 testprefix/share/man/man1/dunstctl.1
+testprefix/share/man/man1/dunstify.1
 testprefix/share/man/man5/dunst.5
 testprefix/share/zsh/site-functions/_dunst
 testprefix/share/zsh/site-functions/_dunstctl