add maps_support/0 function that reports whether jsx was

compiled with maps support or not

README.md

@@ -43,6 +43,7 @@ that
   - [`prettify/1`](#prettify1)
   - [`is_json/1,2`](#is_json12)
   - [`is_term/1,2`](#is_term12)
+  - [`maps_support/0`](#maps_support0)
 * [callback exports](#callback_exports)
   - [`Module:init/1`](#moduleinit1)
   - [`Module:handle_event/2`](#modulehandle_event2)
@@ -609,6 +610,17 @@ returns true if input is a valid erlang representation of json, false if not
 
 what exactly constitutes valid json may be altered via [options](#option)
 
+
+#### `maps_support/0` ####
+
+```erlang
+maps_support() -> true | false
+```
+
+if **jsx** was compiled with map support enabled returns `true`, else
+`false`
+
+
 ## callback exports ##
 
 the following functions should be exported from a **jsx** callback module

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).