Add dnf package manager to Freedoom installer.

linux-game-manager.sh

@@ -519,6 +519,9 @@ case "${game}" in
                 yay -Sy --noconfirm --sudoloop freedoom gzdoom
             elif command -v slapt-get &> /dev/null ; then
                 su -c 'slapt-get -i freedoom gzdoom'
+            elif command -v dnf &> /dev/null ; then
+                sudo dnf copr enable nalika/gzdoom
+                sudo dnf -q -y install freedoom gzdoom
             else
                 dialog --backtitle "Linux Game Manager" --msgbox "No supported package managers found. Please install the freedoom and gzdoom packages manually." -1 -1
                 exit 0