Problem:
commit_chars_str() reads a 0x80-0xBF byte as a 2-byte lead, so
"\xA9x" makes "x" a commit character. nvim_get_hl() returns
a dict, so `#` on it is 0 whether or not the group exists
Solution:
use vim.str_utf_end() and drop entries that are not one whole
character. use next check dict length.
3fa5904cf2