add maps_support/0 function that reports whether jsx was

compiled with maps support or not

src/jsx.erl

@@ -28,6 +28,7 @@
 -export([format/1, format/2, minify/1, prettify/1]).
 -export([encoder/3, decoder/3, parser/3]).
 -export([resume/3]).
+-export([maps_support/0]).
 
 -export_type([json_term/0, json_text/0, token/0]).
 -export_type([encoder/0, decoder/0, parser/0, internal_state/0]).
@@ -161,6 +162,15 @@ resume(Term, {parser, State, Handler, Stack}, Config) ->
     jsx_parser:resume(Term, State, Handler, Stack, jsx_config:parse_config(Config)).
 
 
+-spec maps_support() -> true | false.
+
+-ifndef(maps_support).
+maps_support() -> false.
+-endif.
+-ifdef(maps_support).
+maps_support() -> true.
+-endif.
+
 
 -ifdef(TEST).