other separate, but closely related fixes are:
- fix: The previous fix also solved the (unreported) bug of being unable
to select utf-8 works by double-clicking.
- fix: The move to next/previous word (Ctr-arrow) behaved differently
depending on the direction. I made both the move left/right functions
share a much simpler algorithm and rewrote the find start/end of word
functions share the same code structure.
### Problem description
The code was using the byte index of the match into the utf-8 string to
store the match locations, but the code that sets the selection uses the
char index into the utf-8 string instead. Another problem was that the
search uses the byte index to determine if it needs to find more
matches.
### Implementation description
Both problems were solved by introducing two functions to switch from
coordinates in units of bytes to coordinates in units of chars and vice
versa.
Co-authored-by: Nik <werwolv98@gmail.com>
3c060cc57a