Document changes and release 5.13.19pureos2 of linux-librem5

Signed-off-by: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@puri.sm>
2 jobs for rel5.13.19pureos2 in 70 minutes and 38 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #369726
librem5
build:aarch64

00:20:33

passed #369727
librem5:arm64
build:deb

01:10:37