feat: add kebab_case and screaming_snake_case string helper

• Add kebab_case function for converting strings
• Add screaming_snake_case function for converting strings
• Update GitHub Actions CI workflow
• Fix and improve documentation formatting

Introduce general utilities and refactor core modules

• Added tap func for inline value inspection without breaking functional chains
• Added retry func for retrying fallible operations with optional backoff strategies
• Introduced async_retry func behind the async_retry feature flag (requires Tokio)
• Updated Cargo.toml to support optional async feature using Tokio
• Grouped general-purpose utilities under a general module for improved modularity
• Moved array module contents to a new collection module
• Moved condition module into the general module
• Added omit_keys and pick_keys functions to the collection module
• Added snake_case, slugify, safe_parse, and truncate_middle utilities to the string module
• Added Transform trait with reusable string methods