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 Job ID Name Coverage
  Test
manual #40210
allowed to fail manual
build:arch
passed #40206
build:asan

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passed #40209
build:bionic

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passed #40208
build:buster

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passed #40207
build:stretch

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passed #40205
build:ubsan

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