Document changes and release 5.13.16pureos1 of linux-librem5

Signed-off-by: Martin Kepplinger <martin.kepplinger@puri.sm>
2 jobs for release51316_1 in 70 minutes and 38 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Build
passed #366969
librem5
build:aarch64

00:36:23

passed #366970
librem5:arm64
build:deb

01:07:53