Add changesets and configure github workflow

[elboletaire]

This may not be possible until we publish version 1.0.0 of the packages (I think changesets is prepared for stable versions, not for beta ones [<1.0]).

https://github.com/changesets/changesets/blob/main/docs/intro-to-using-changesets.md

Doing so, all the versioning and publishing to npmjs would be automated, reducing the workload.