* Added openarray[char] overloads to std/unicode
Call substr instead of index slice inside unicode
Added substr overload for openarray for parity with string functionality
Made style checker happies and fixed overloads for substr
* Added update to changelog [skip ci]
* Inline unicode string operations
* Moved substr overload to unicode
Co-authored-by: Andreas Rumpf <rumpf_a@web.de>