Integrate changesets action to net-changesets

[magiino]

Use https://github.com/changesets/action in this repo for versioning and setup https://github.com/changesets/bot to check PRs.

[trueberryless]

This sounds very interesting.

I am just wondering how this will work. But I didn't look at all if the JS implementation is compatible with other languages as well, I guess it probably is.

Just one more thought: I personally always found it confusing in my Node projects, that the action is actually used for two things:

1. Creating PRs based on the changeset files that update versions and generate the CHANGELOG.md
2. Publishing the actual packages when no changeset files exists.

This just feels a little fragile to me, as I wouldn't expect that packages get published every time I have no changeset files, but I might miss some implementation details here. This might also be worth thinking about in a dedicated issue, but for now I thought it fits here as the decision whether to use the existing action or create a dedicated one is related.

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Awesome project btw, I always wished there was a .NET port for changesets 🙌