Add dbt 1.6, update readme and add windows tests

[alanmcruickshank]

The README was out of date with the supported versions, so this updates that.

It also adds test coverage for dbt 1.6 (the latest version https://pypi.org/project/dbt-core/).

Perhaps more experimentally, I've also added a windows test run (although, there's a good chance this might fail the first run through the github action).

I'm happy to help debug the windows test to get it working.

[alanmcruickshank]

I don't think I have access to approve the workflows, but feel free to tag me if anything fails and I can help fix it 👍.

[syou6162]

@alanmcruickshank The test with dbt 1.6 is failing, so it looks like Makfile needs to be modified as well.

https://github.com/z3z1ma/dbt-core-interface/blob/main/Makefile#L61-L86