Add initial version of entities

pom.xml

src/main/java/com/example/demo/DemoApplication.java

src/main/java/com/example/demo/domain/AssessmentLevel.java

src/main/java/com/example/demo/domain/BaseLevel.java

src/main/java/com/example/demo/domain/GameLevel.java

src/main/java/com/example/demo/domain/Hint.java

src/main/java/com/example/demo/domain/InfoLevel.java

src/main/java/com/example/demo/domain/Person.java

...om/example/demo/repository/AssessmentLevelRepository.java

...java/com/example/demo/repository/BaseLevelRepository.java

...java/com/example/demo/repository/GameLevelRepository.java

...in/java/com/example/demo/repository/PersonRepository.java