Add a separate import group for jakarta imports

We currently have [4 groups](https://github.com/spring-io/spring-javaformat/blob/492d2f58c79e596bcee3ec1ff73d5f6010f8207b/spring-javaformat/spring-javaformat-checkstyle/src/main/java/io/spring/javaformat/checkstyle/check/SpringImportOrderCheck.java#L42):

- `java`
- `^javax?\.`
- `*`
- Project's root package

I wonder if we should add another for `jakarta.` imports.