Multiple improvements in tird.py:

- Add `SECURITY.md`.
- Add `-d/--debug` option.
- Add type hints to Python code.
- Update color scheme for Linux terminal emulators.
- Improve handling of possible I/O errors.
- Remove personalization for keyed BLAKE2b (MAC).
- Remove personalization for BLAKE2b in modes 4, 5.
- Run garbage collection when keys are no longer needed (use `del` and `gc.collect()`).
- Add authentication tag by default.
- Change randomized padding scheme.
- Rename `metadata` to `comments` and make its size non-customizable (always 512 bytes).
- Set new `scrypt` parameters: n=2**20, r=8, p=1.
- Add salt when hashing keyfiles and passphrases using BLAKE2b.
- Set new salt sizes for KDF functions: 16 bytes.
- Add `catpig` v0.3.0 memory-hard password-hashing function before `scrypt` KDF.
- Show padding positions in modes 2, 6.
- Cipher simplification. Removing rounds, reducing block size to 64K. Now the ciphertext is obtained by XORing plaintext with the output of SHAKE256. This also results in easier handling of keyfiles.
- Remove custom options: `Debug`, `Number of rounds`, `Keystream block size`, `Randomized padding order`, `Derived key length`, `Metadata size`.
- Add new cusom options: `Catpig KDF space`, `Catpig KDF passes`.