Add note about depth 0 in Finder

Author: tmotyl

components/finder.rst

@@ -311,6 +311,8 @@ Restrict by a depth range by chaining calls or passing an array::
 
     // same as above
     $finder->depth(['> 2', '< 5']);
+    
+Depth 0 means direct children (files and folders).
 
 Custom Filtering
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