Support gradle configuration cache

[tnielens-centrica]

I'm facing configuration cache issues when applying your plugin.

- Task `:my-project:jaxbJavaGenV1311` of type `com.intershop.gradle.jaxb.task.SchemaToJavaTask`: invocation of 'Task.project' at execution time is unsupported.
  See https://docs.gradle.org/8.5/userguide/configuration_cache.html#config_cache:requirements:use_project_during_execution

To reproduce, run jaxbJavaGen<name> with --configuration-cache on any project using this plugin. Gradle version 8.5.

The gradle configuration cache complements the task cache and enables important speed-ups in large multi-module projects.

[tnielens-centrica]

Relates to #59.