Document changes and release 5.13.1pureos1~amber1 of linux-next-librem5

Signed-off-by: Martin Kepplinger <martin.kepplinger@puri.sm>
2 jobs for next/amber-phone in 68 minutes and 20 seconds (queued for 24 minutes and 31 seconds)
Status Job ID Name Coverage
  Build
passed #358907
librem5
build:aarch64

00:23:51

passed #358908
librem5:arm64
build:deb

01:08:20