feat: custom grub bootloader - bee branding, 5s auto-boot, no splash

iso/builder/config/bootloaders/grub-pc/config.cfg

@@ -0,0 +1,27 @@
+set default=0
+set timeout=5
+
+if [ x$feature_default_font_path = xy ] ; then
+    font=unicode
+else
+    font=$prefix/unicode.pf2
+fi
+
+if loadfont $font ; then
+    set gfxmode=800x600
+    set gfxpayload=keep
+    insmod efi_gop
+    insmod efi_uga
+    insmod video_bochs
+    insmod video_cirrus
+else
+    set gfxmode=auto
+    insmod all_video
+fi
+
+insmod gfxterm
+insmod png
+
+source /boot/grub/theme.cfg
+
+terminal_output gfxterm