Sourceset sizes

On validating HTML (Ready to check - Nu Html Checker) I get the following result with an image placed with Sitecake:
»When the srcset attribute has any image candidate string with a width descriptor, the sizes attribute must also be present.«
I found this code example (Responsive Images - The srcset and sizes Attributes):

<img src=“one.png”
srcset=“two.png 100w, three.png 500w, four.png 1000w”

 sizes="(min-width: 900px) 1000px,
        (max-width: 900px) and (min-width: 400px) 50em,
        ( not (orientation: portrait) ) 300px,
        ( (orientation: landscape) or (min-width: 1000px) ) 50vw, 

Where can I define this in sitecake? Cannot find it in Docs :grimacing:

Thanks and have a nice day,

In sitecake/config.php there is a setting

 * Max relative diff (in percents) between two image widths in pixels
 * so they could be considered similar
$config['image.srcset_width_maxdiff'] = 20;

This might help.