Invalid delta Length and also Delta.slice() breaks latin unicode char in two parts e.g. ő

[khaled4vokalz]

Reproduction Steps:

1. Enter latin character ő in Quill
2. delta.length() returns 2
3. range returns 1 as index if the cursor is after the latin character
4. delta.slice(0, range.index) returns 'o' only not the whole character

IMO, if the range returns 1 then delta.slice() should also behave accordingly. Now I'm not sure how to correctly split the delta when this type of unicode characters are used as delta