r.neighbors.html: annulus shaped neighborhood example added

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@61208 15284696-431f-4ddb-bdfa-cd5b030d7da7

raster/r.neighbors/r.neighbors.html

@@ -206,6 +206,16 @@ This corresponds to the following 3x3 matrix:
     -------
 </pre>
 
+To calculate an annulus shaped neighborhood the contents of weight.txt file 
+may be e.g. for size=5:
+<pre>
+ 0 1 1 1 0
+ 1 0 0 0 1
+ 1 0 0 0 1
+ 1 0 0 0 1
+ 0 1 1 1 0
+</pre>
+
 The way that weights are used depends upon the specific aggregate
 (<b>method</b>) being used.