Add grub config for Ubuntu

iso/boot/ubuntu/grub.cfg

@@ -0,0 +1,25 @@
+set timeout=30
+
+loadfont unicode
+
+set menu_color_normal=white/black
+set menu_color_highlight=black/light-gray
+
+menuentry "Install Dappnode (over Ubuntu Server)" {
+        set gfxpayload=keep
+        linux   /casper/vmlinuz autoinstall --- # Added autoinstall to make it unattended
+        initrd  /casper/initrd
+}
+grub_platform
+if [ "$grub_platform" = "efi" ]; then
+menuentry 'Boot from next volume' {
+        exit 1
+}
+menuentry 'UEFI Firmware Settings' {
+        fwsetup
+}
+else
+menuentry 'Test memory' {
+        linux16 /boot/memtest86+x64.bin
+}
+fi