possible changelog + upgrade guide for v6

[illusionalsagacity]

I don't know if you'd prefer to write these by hand, but I prompted this from the following:

your goal is to research and document the changes for this git HEAD to the v5.1.3 tag. The overall change between then is for this rescript bindings library to support @mui/material v6. So your audience for the changes is
rescript developers who were previously using 5.1.3. You should assume the developers reading this changelog have familiarity with the underlying @mui/material v6 breaking changes, so you can briefly mention them instead
of going into details. Make sure you read the git commits for merges in detail and summarize each before proceeding. Then take all of this context and refine it to generate changelog entries how @CHANGELOG.md is
formatted today.

Nice, now using this changelog, can you create an upgrade guide please

[fhammerschmidt]

It's fine when those are generated but then I would need some sort of confirmation that the information in the guide is correct.