Add OpenBSD logo

Author: ibara

download.dd

@@ -239,6 +239,7 @@ Macros:
         NIX=$(LOGO nix, Nix/NixOS)
         SNAP=$(LOGO snapcraft, Snap)
         WINDOWS=$(LOGO windows, Windows)
+        OPENBSD=$(LOGO openbsd, OpenBSD)
 
         LINK_OS=<a href="$(ROOT_DIR)dmd-$1.html" style="text-decoration: none" title="$3 setup and usage information">$2</a>