Mintotp

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Added

- Add license information in package metadata.
- Add `digits` and `digest` to `totp()` parameter list.
- Add command line arguments for time-step, digits, and digest.

Changed

- Rename `secret` to `key` in `hotp()` and `totp()` parameter lists.
- Rename `interval` to `time_step` in `totp()` parameter list.

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Added

- Add a minimal TOTP generator.
- Expose `hotp()` and `totp()` as module-level functions.
- Add project documentation.