feat(pastes): use rustler for highlight NIF

Signed-off-by: SphericalKat <amolele@gmail.com>

lib/ketbin/utils/syntax.ex

@@ -2,5 +2,9 @@ defmodule Ketbin.Utils.Syntax do
   use Rustler, otp_app: :ketbin, crate: "ketbin_utils_syntax"
 
   # When your NIF is loaded, it will override this function.
-  def add(_a, _b), do: :erlang.nif_error(:nif_not_loaded)
+  def add(_a, _b), do: error()
+
+  def highlight_text(_text, _lang), do: error()
+
+  defp error(), do: :erlang.nif_error(:nif_not_loaded)
 end