Operation request: <Substitution with extra bytes>

## Summary
Hi there. Again, thank you for making and developing Cyberchef. I have difficulty making substitutions where I want to substitute one character with two characters. The cipher substitutions just tell me:
"Warning: Plaintext and Ciphertext lengths differ" and it only substitutes the first of the two or more of the substitution.

I understand why this is the case but isn't there an alternative or some way of making such substitutions?

### Example Input
ⴉ
### Example Output
к
### Required Output
кӏ

Start by reproducing the example in CyberChef's Cipher substitutions operation and inspect how it handles unequal plaintext and ciphertext lengths. The change is done when one input character can produce the requested two-character output without the current warning or truncation, while existing substitutions continue to work.

Written by the indexing model from the issue text.