merge different selectors with similar properties

[yairEO]

Turn this:

a{ color:red; opacity:1; background:blue; }
b{ color:red; opacity:1; background:blue; height:10px; }

To this:

a,b{ color:red; opacity:1; background:blue; }
b{ height:10px; }

But only if it's "worth it" meaning, bytes were saved. in some situations the selector might be too long and not worth it:

a{ color:red; opacity:1; background:blue; }
.this_is_a_very > .long_selector ~ ul.drop_down_selector > li.list_item b{ color:red; opacity:1; background:blue; }

in the above example it's not worth repeating that long selector again, just to merge it's properties with a selector. it would result in a larger output.

This would eliminate the need to use extend methods in pre-processors manually and ease the workflow.