Reorganize code and document functions

lib/repl.ml

@@ -0,0 +1,15 @@
+let rec loop state =
+  print_string "inspector> ";
+  flush stdout;
+  try
+    match read_line () |> String.lowercase_ascii with
+    | "exit" | "quit" -> print_endline "bye"
+    | "next" -> loop (State.next state)
+    | "prev" -> loop (State.prev state)
+    | "show" ->
+        Printf.printf "[%d]: %s\n" (State.cursor state) (State.show_line state);
+        loop state
+    | str ->
+        print_endline str;
+        loop state
+  with End_of_file -> print_endline "bye"