Helper for Js_of_ocaml Toplevel.

`val use : Stdlib.Format.formatter -> string -> bool`

`use fmt content` Execute commands `content`. It does not print types nor values.

`val execute : bool -> ?pp_code:Stdlib.Format.formatter -> ?highlight_location:(Location.t -> unit) -> Stdlib.Format.formatter -> string -> unit`

`execute print fmt content` Execute `content`. `print` says whether the values and types of the results should be printed. `pp_code` formatter can be use to output ocaml source during lexing.

`val initialize : unit -> unit`

Initialize Js_of_ocaml toplevel.