There is nothing built in, but you can easily do it with a little scripting.
Some starting points:
liquibase.parser.ChangeLogParserFactory.getInstance().getParser(".xml", resourceAccessor).parse(...)
will return a DatabaseChangeLog object representing the changelog file.
liquibase.serializer.ChangeLogSerializerFactory.getInstance().getSerializer(".yaml").write(...)
will output the changeSets in the DatabaseChangeLog object out to a file in yaml format