The termwiz Modifiers type isn't the right one!
Use the input layer types instead, and then we get the correct
string formatting.
refs: https://github.com/wez/wezterm/issues/3434
According to its benchmarks, it's almost 2x faster than
unicode_segmentation. It doesn't appear to make a visible
difference to `time cat bigfile`, but I'll take anything
that gives more headroom for such little effort of switching.
