Added @phpver to document the php compatibility

README.md

@@ -6,6 +6,7 @@
  @package  OpenGallery   http://github.com/par7133     
  @author   Daniele Bonini <my25mb@aol.com>      
  @version  1.0     
+ @phpver   5.6 to 7.3      
  @access   public     
  @note The class rendering the output controls is making use of Bootstrap.     
  Furthermore, FastPagination is making use of the class FastErr part of OpenGallery