Accessing a string using array brackets is not multi-byte safe

[hxss]

php-finediff/src/Render/Renderer.php

Line 31 in 80b04a8

$opcode = $operationCodes[$operationCodesOffset];

Hello. Please replace the offset operator with mb_substr. I have an issue with emoji or cyrillic symbols that uses more than 1 byte.

[mrdan]

If you submit a PR that would speed things up, otherwise it might be a little while before we get to this