feat(cli): enhance CLI flexibility and fix option precedence

- Exposed library configuration options (delimiter, case mode, strictness, etc.) as CLI flags in `cli/main.go`.
- Regenerated CLI command implementations using `gosubc` to support the new flags.
- Refactored `strings2` helper functions (`ToCamel`, `ToSnake`, etc.) in `permutations.go` and `types.go` to apply default options before user options, allowing users to override defaults.
- Updated `process` function in `cli/main.go` to pass parsed options to `strings2` functions as variadic arguments.
- Added a section to `README.md` about the CLI mode.

Author: google-labs-jules[bot]