Increased code quality
- [!!!] "bool" is now consequently used instead of "boolean". Although this makes no difference for the serializer and IDEs, it may break packages parsing the doc blocks. This is the only reason for a new version.
- added GitHub workflow actions to automate all the checks
- removed unused code and refactored the ApiGenerator by moving code to a TypeUtil class
- added test cases for 100% code coverage
- added more tests for 100% mutation coverage