fix: Adds copy task for graphviz.dat to epl build

[childenProtos]

Fixes #1517

[arnaudroques]

Thanks for helping us on this subject.
However, it seems that the build fail. Any thought about it?

[The-Lum]

FYI, here is the error stack:

• https://github.com/plantuml/plantuml/actions/runs/6096155472/job/16541613348?pr=1530

* What went wrong:
A problem was found with the configuration of task ':plantuml-epl:sourcesJar' (type 'Jar').
  - Gradle detected a problem with the following location: '/home/runner/work/plantuml/plantuml/plantuml-epl/build/copiedResources'.
    
    Reason: Task ':plantuml-epl:sourcesJar' uses this output of task ':plantuml-epl:copyGraphizBinToGenerated' without declaring an explicit or implicit dependency. This can lead to incorrect results being produced, depending on what order the tasks are executed.
    
    Possible solutions:
      1. Declare task ':plantuml-epl:copyGraphizBinToGenerated' as an input of ':plantuml-epl:sourcesJar'.
      2. Declare an explicit dependency on ':plantuml-epl:copyGraphizBinToGenerated' from ':plantuml-epl:sourcesJar' using Task#dependsOn.
      3. Declare an explicit dependency on ':plantuml-epl:copyGraphizBinToGenerated' from ':plantuml-epl:sourcesJar' using Task#mustRunAfter.
    
    For more information, please refer to https://docs.gradle.org/8.3/userguide/validation_problems.html#implicit_dependency in the Gradle documentation.

Regards,
Th.

[arnaudroques]

Very nice.
That's great, many thanks for your help!