feat: Gradle plugin implementation

[nandorholozsnyak]

New Gradle plugin extension point for the tool.

Please check the documentation and samples.

Closes #6 .

[nandorholozsnyak]

@all-contributors please add @tkhadir for code

[allcontributors]

@nandorholozsnyak

I've put up a pull request to add @tkhadir! 🎉

[nandorholozsnyak]

Hello @tkhadir,

Thank you for your initial work on the plugin, it was reworked, documentations were added and some samples are available.

It will be released in the upcoming days.

[nandorholozsnyak]

The Gradle plugin was born! Initialization and prototype for single documentation generation were done, and AggregationDocumenter was setup properly. A new XSD was introduced to fix the properties attribute issue. Simple documentation task, aggregation task, and samples were added, and documentation and samples were changed. CI steps and README.adoc were updated, and finally, cleanup and README changes were made. The plugin was complete!
_{Created by Commit Teller}

[nandorholozsnyak]

The team had been working hard the last few weeks on a new gradle plugin. After many commits and pull requests, finally the plugin was ready for production. The first feature was adding the gradle plugin itself, and the second was setting up a prototype for single documentation generation.

The team then encountered a few issues, but they were quickly resolved. First, they noticed the AggregationDocumenter was not setting up the exclusion and inclusion lists properly. After making the necessary changes, they found their 0.4.0 XSD was not handling the properties attribute correctly, and they had to introduce a new XSD to fix the problem.

With all the fixes in place, the team then moved on to the next feature: adding a simple documentation task, an aggregation task, and some samples. After making the necessary changes and typos fixes in the Maven plugin documentation, they merged the branch into feature/gradle-plugin and did some CI steps and README changes. Lastly, the team did some cleanup and made changes to the README file.

Finally, after all the hard work and debugging, the team was ready to launch their new gradle plugin. With it, users would now be able to easily generate single documentation, as well as aggregate multiple documents with the help of funny samples. It was a great success!
_{Created by Commit Teller}