test: test_bem improvement

fix: Remove unsupported get_params method call in test assertion

fix: Modify test to use `.block` property when calling Build object

fix: Resolve module import issue with block names containing slashes

feat: Enhance test_bem with comprehensive BEMPy library testing

docs: Simplify README to focus on core library information

fix: Add mana attribute to Elf race modifier

fix: Add fertility attribute to female gender modifier

fix: Add level attribute to Character class in init method

fix: Add init method to modifier classes to resolve AttributeError

test: Add comprehensive test suite for BEMPy core functionality

fix: Resolve database connection and block reference issues in backend

refactor: Enhance backend block tests with comprehensive coverage and detailed assertions

docs: Create comprehensive API documentation for all public classes and functions

refactor: Improve code comments and structure in block class initialization