add onfullscreen & onfullscreenExit event handle

dist/js/editormd.js

@@ -65,6 +65,8 @@
         watch                : true,  
         onload               : function() {},
         onchange             : function() {},
+        onfullscreen         : function() {},
+        onfullscreenExit     : function() {},
         toc                  : true,
         tocStartLevel        : 2,
         fontSize             : "13px",
@@ -1295,14 +1297,15 @@
                     width    : $(window).width(),
                     height   : $(window).height()
                 }).addClass(fullscreenClass);                                             
+
+                this.resize();
+                $.proxy(this.settings.onfullscreen, this)();            
             }
             else
             {                
                 this.fullscreenExit();             
             }
 
-            this.resize();
-
             $(window).keyup(function(event) {
                 if (_this.state.preview) {
                     return ;                
@@ -1343,6 +1346,8 @@
 
             this.resize();
             
+            $.proxy(this.settings.onfullscreenExit, this)();
+
             return this;
         }
     };