"Hardcode" pkl version somewhere instead of GitHub action input

[StefMa]

Right now it is not visible for consumers what pkl version is used when using the pkl-eval node package.
If I get it right, this repo uses GitHub actions input for that.
When doing a release, you can put the pkl version as input and it will does everything on the fly.

I think it makes more sense to "hardcode" somewhere the pkl version that is used for that release so it is more visible ofr consumers.

Alternative:
You use the same version schema as pkl 🙃