Add doc_items help page

depends.txt

@@ -1,2 +1,3 @@
 treasurer
 intllib?
+doc_items?

init.lua

@@ -126,4 +126,10 @@ do
 		end,
 	}
 	minetest.register_node("tsm_surprise:question",nodedef)
+
+	if minetest.get_modpath("doc_items") then
+		doc.sub.items.set_items_longdesc({
+			["tsm_surprise:question"] = S("If this block is mined, a few surprise items may drop out of it."),
+		})
+	end
 end

locale/de.txt

@@ -1 +1,2 @@
 Surprise block=Überraschungsblock
+If this block is mined, a few surprise items may drop out of it.=Wenn dieser Block abgebaut wird, könnten ein paar Überraschungen hinausfallen.

locale/template.txt

@@ -1 +1,2 @@
-Surprise block
+Surprise block =
+If this block is mined, a few surprise items may drop out of it. =