Illustrate `format_on_save` external command using prettier

This gives us a chance to highlight a real-world scenario that a lot
of our users will want to use, as well as showcasing the special
`{buffer_path}` argument.
b5765bc8cdAntonio Scandurra committed on 7/15/2022, 7:00:10 AMparentd89465c
1 file changedLine totals unavailable