API surface and versioning

[csmith]

It seems that 1.4.2 removed the util.DedentPosition func. As this is exposed publicly it could be considered a breaking change, and under semantic versioning would necessitate a major version bump. It has in fact broken goldmark-mathjax as it calls this method: https://github.com/litao91/goldmark-mathjax/blob/a43cf739a50fb884a05e49f65ea60a3fa9aa4203/block.go#L60

It seems like there are three possible situations here:

1. The breaking change was made unintentionally and should have been held back for a future major version
2. The util package isn't meant to be used externally, so breaking changes there are fair game
3. goldmark's versions aren't meant to be semantic and any release may break compatibility

In the case of 2 or 3 it would be good if this was documented somewhere (e.g. in the README) as it's a bit surprising to be broken by a patch release.