isByteLength function
Checks if the string's UTF-8 byte length falls in a range.
The byte length must be at least min. If max is provided, it must
also be at most max.
Example:
isByteLength('abc', 2); // true
isByteLength('abc', 4); // false
isByteLength('é', 1, 2); // true ('é' is 2 bytes in UTF-8)
Implementation
bool isByteLength(String str, int min, [int? max]) =>
_isByteLength(str, min, max);