update readme

Author: nahid

README.md

@@ -148,6 +148,7 @@ Following API examples are shown based on the sample JSON data given [here](exam
 * [whereStartsWith](#wherestartswithkey-val)
 * [whereEndsWith](#whereendswithkey-val)
 * [whereContains](#wherecontainskey-val)
+* [whereMatch](#wherematch-val)
 * [sum](#sumproperty)
 * [count](#count)
 * [size](#size)