feat: Add CRTP pattern Ref: #2342 (#2580)

* Add crtp directory with builder for object hierarchy example Ref: #2342

* Add space package Ref: #2342

* Add comments for checkstyle Ref: #2342

* Add fight package as second crtp example Ref: #2342

* Add README.md Ref: #2342

* Add use cases examples in README.md for crtp Ref: #2342

* Remove space package Ref: #2342

* Move files from fight package to crtp Ref: #2342

* Add real world example in README.md Ref: #2342

* Update crtp README.md Ref: #2342

* Delete FighterTest Ref: #2342

* Update App and AppTest in crtp Ref: #2342

* Add category and tag in README.md frontmatter Ref: #2342

* Add @Data annotation and remove constructor and toString in MmaFighter Ref: #2342

* Add FightTest Ref: #2342

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Co-authored-by: Antonio Addeo <an.addeo@reply.it>