How to set the zIndex layer order for geoJson layers? : <p>I would like to have certain layers to be always on top of others, no matter in which order they are added to the map. 
I am aware of <code>bringToFront()</code>, but it does not meet my requirements. I would like to set the zIndex dynamically based on properties.</p>

<p>Leaflet has the method <code>setZIndex()</code>, but this apparently does not work for geoJson layers:
<a href="https://jsfiddle.net/jw2srhwn/" rel="noreferrer">https://jsfiddle.net/jw2srhwn/</a></p>

<p>Any ideas?</p>
