docs/Generator: Added SmallFoliage illlustrations.

docs/Generator.html

@@ -483,6 +483,10 @@ height to find the third coord. If we want to generate clumps of mushrooms in th
 generate the clump center coords in 3D and either use 3 offsets for the mushrooms, or use 2 offsets plus
 searching for the closest opening Y-wise in the terrain.</p>
 
+<p>Note that the clumps generated by this scheme may overlap several chunks. Therefore it's crucial to
+actually check the surrounding chunks if their clumps overlap into the currently generated chunk, and apply
+those as well, otherwise there will be visible cuts in the foliage along the chunks borders.</p>
+
 <h3>Springs</h3>
 <p>Water and lava springs are essential for making the underground quite a lot more interesting. They are
 rather easy to generate, but a bit more difficult to get right. Generating simply means that a few random