Add docker labels to have update tools be able to pull changelog/release notes

[halkeye]

For example https://docs.renovatebot.com/modules/datasource/docker/

but other tools will pull those same labels

[halkeye]

Apparently it pulls the difference between "latest" and the latest tag? not 100% sure

$ regctl image config --format '{{ jsonPretty .Config.Labels }}' stashapp/stash
null

[WithoutPants]

I believe this is incomplete. The build dockerfiles are only used when building manually. The ci dockerfile is used by GitHub actions to deploy to docker hub. The build github actions file will also need to be updated to set the appropriate environment variable.

[halkeye]

oh wow I can't believe i missed the build in https://github.com/stashapp/stash/blob/develop/docker/ci/x86_64/docker_push.sh
I'll get that second dockerfile updated

[halkeye]

is there any easy way for me to confirm this ahead of time? I kinda did it blind