"more boxes" perk.

Obtained at 3 accepted boxes.

Grants 5 boxes as build max, up from 3.

mods/boxes/nodes.lua

@@ -433,6 +433,28 @@ local function grant_perks(box_id, boxes)
 			})
 		end
 	end
+	if accepted >= 3 then
+		local limit = tonumber(builder:get_attribute("box_create_limit") or "3")
+		if limit <= 3 then
+			minetest.log("perks: granted more boxes to " .. builder)
+			announce.all(builder .. " has been granted the more boxes perk!")
+			telex.send({
+				to = builder,
+				from = "sofar",
+				subject = "Congratulations! You've been awarded a perk!",
+				content = {
+					"Dear player,",
+					" ",
+					"We really appreciate the hard work you put in building boxes.",
+					" ",
+					"As a thank you, you have been granted the \"more boxes\" perk!",
+					" ",
+					"--sofar"
+				}
+			})
+			builder:set_attribute("box_create_limit", "5")
+		end
+	end
 	if accepted >= 5 then
 		local privs = minetest.get_player_privs(builder)
 		if not privs.sprint then