nextBoundary
Look for the next extended grapheme cluster boundary in a CharSequence. It assumes the start of the char sequence at offset off is a boundary.
See Unicode Standard Annex #29 Unicode Text Segmentation for the specification for the extended grapheme cluster boundary rules. The following implementation is based on the annex for Unicode version 15.1.
Return
the next grapheme boundary
Parameters
src
the CharSequence to be scanned
off
offset to start looking for the next boundary in the src
limit
limit offset in the src (exclusive)