Update changelog

This is mainly to give me a version number I can use in other packages'
dependencies.

Signed-off-by: Simon McVittie <smcv@collabora.com>
6 jobs for cmp-by-elf in 8 minutes (queued for 3 seconds)
Status Name Job ID Coverage
  Test
manual build:arch #40210
allowed to fail manual
passed build:asan #40206

00:02:54

passed build:bionic #40209

00:07:35

passed build:buster #40208

00:08:00

passed build:stretch #40207

00:07:35

passed build:ubsan #40205

00:02:49