Restore accidentally removed the initramfs boot warning banner.
Ref: 8055acc9be (commitcomment-73447330)
Fixes: 8055acc9be ("luci-theme-bootstrap: overhaul styles")
Signed-off-by: Jo-Philipp Wich <jo@mein.io>
(cherry picked from commit 56fab648caa78422aac47ab8cec168e8a0999316)