Merge branch 'version-add-remove-button' into 'dev'

add version on new attr (class-add/remove)

See merge request !77

source/import_documentation/Mixins/widget-mixin.rst

@@ -215,7 +215,9 @@ Attributes
 - ``multiple-[field]-add-label`` : Text of the “+” button used to add an element  
 
 - ``multiple-[field]-remove-label`` : Text of the “x” button used to remove an element  
-    
-- ``multiple-[field]-add-class`` : Class of the “+” button used to add an element  
 
-- ``multiple-[field]-remove-class`` : Class of the “x” button used to remove an element  
+*Available from version 0.18*
+
+- ``multiple-[field]-add-class`` : Class of the “+” button used to add an element
+
+- ``multiple-[field]-remove-class`` : Class of the “x” button used to remove an element  
\ No newline at end of file