This pull request introduces significant changes to thephper project, adding support for PHP enums, improving documentation, and making several internal adjustments to enhance functionality and maintainability.

Enum Support:

• Added a new modulephper::enums to provide Rust wrappers for PHP enum functionality, supporting pure enums, integer-backed enums, and string-backed enums.
• Updatedphper-build/src/lib.rs to include configuration forphper_enum_supported when PHP version is 8.1 or higher.
• Included documentation on how to register enums inphper-doc/doc/_06_module/_08_register_enum/index.md.
• Modifiedphper-doc/src/lib.rs to include the new enum registration documentation module.
• Added necessary includes for enums inphper-sys/php_wrapper.c.

Documentation and Configuration:

• EnhancedCargo.toml to include thesealed crate and updated documentation configurations.[1][2]
• Enabled conditional compilation attributes for documentation inphper/src/lib.rs.

Internal Adjustments:

• Made several internal structs and functions inphper/src/classes.rs public within the crate for broader usage.[1][2][3][4][5]
• IncludedEnumEntity in thephper/src/modules.rs module imports.