Install release-plz to simplify release procedure

[jdrouet]

In order to simplify the release workflow, we should create a github action with release-plz.
This way, it will automagically open a PR to release with the adequate version.

[pront]

I have an untested draft PR to do that:
https://github.com/vectordotdev/vrl/pull/877/files

But feel free to explore other options :)

[jdrouet]

I don't know if you have tried release-plz. It's fairly simple, you put a github action configuration that will run on the main branch, that will open a PR to bump the version each time you do a change. It can detect breaking changes and knows what kind of version bump to make.
If you merge that PR, then the same github action configuration will create a github release and push the changes to crates.io.

I've been using it on some of my crates like serde-toml-merge and mrml.

I'll open a PR with the change but I'll need a crates.io token with write access to VRL.