Is your feature request related to a problem? Please describe.
It would be really useful if ocamlformat could handle files with #use "foo.ml" in them.

#523 mentions that shebangs #!/usr/bin/env ocaml and #require "Foo" are supported, and #731 mentions some others, but #use currently isn't supported.

#use "bar.ml"

$ ocamlformat --enable-outside-detected-project ~/tmp/foo.ml
ocamlformat: ignoring "/Users/wilfred/tmp/foo.ml" (syntax error)
File "/Users/wilfred/tmp/foo.ml", line 1, characters 0-1:
Error: Syntax error

Describe the solution you'd like
Format files with `#use "foo.ml" in them. I don't think ocamlformat needs to anything with the directive, but it would be nice if it processed the rest of the file.