Update simple-map.php

Added support to parse shortcode content to display in a gmaps.js infowindow.

Altered following lines:

after line 134 (`$lng = $p['lng'];`) i've added `$cnt = do_shortcode($content);` to define a new variable.

in line 143 (144 after adding above line) i've added `data-cont="%s"` making the whole line look like this: `'<div class="%s"><div data-breakpoint="%s" data-lat="%s" data-lng="%s" data-zoom="%s" style="width:%s;height:%s;" data-cont="%s">%s</div></div>',` and after line 150 (newly 151) I've also added `$cnt,` to pass the above created variable for the jQuery code to process.