Automate releases

[johanhelsing]

It would be good if there were fewer manual steps involved in releasing.

Current manual steps:

1. Update bevy version support table in readme
2. Release on crates.io

   cargo release minor -p matchbox_socket -p matchbox_protocol -p matchbox_server -p matchbox_signaling -p bevy_matchbox --execute

3. Tag commit with simple prefix (e.g. v0.9.0)

   git tag v0.9.0
   git push origin v0.9.0

4. Push matchbox_server docker image to dockerhub

   docker pull ghcr.io/johanhelsing/matchbox/matchbox_server:v0.9.0
   docker image tag ghcr.io/johanhelsing/matchbox/matchbox_server:v0.9.0 jhelsing/matchbox-server:v0.9.0
   docker image tag jhelsing/matchbox-server:v0.9.0 jhelsing/matchbox-server:latest
   docker push jhelsing/matchbox-server:v0.9.0
   docker push jhelsing/matchbox-server:latest

5. Publish new example builds (some work done in #212 )
6. Publish github release (this should perhaps be manual, the merge list is usually quite noisy)

[simbleau]

Best to do these steps in a GitHub Action triggered on a "v*" release. This is what I do to publish packages, e.g. https://github.com/vectorgameexperts/bevy-async-task/blob/main/.github/workflows/release.yml

[AgustinRamiroDiaz]

@johanhelsing are you still interested in this? I could help with parts of this issue, with the approach that @simbleau proposed

[simbleau]

Sure!