Add and edit fuel registrations

Edited fuels: fences, wooden ladder.
New fuels:
boat, paper, book, dry shrub, stick, vessels shelf, wooden tools,
wooden door, trapdoor, fence gates, farming crops, stairs, slabs, beds.

mods/stairs/init.lua

@@ -106,6 +106,20 @@ function stairs.register_stair(subname, recipeitem, groups, images, description,
 				{recipeitem, recipeitem, recipeitem},
 			},
 		})
+
+		-- Fuel
+		local baseburntime = minetest.get_craft_result({
+			method = "fuel",
+			width = 1,
+			items = {recipeitem}
+		}).time
+		if baseburntime > 0 then
+			minetest.register_craft({
+				type = "fuel",
+				recipe = 'stairs:stair_' .. subname,
+				burntime = math.floor(baseburntime * 0.75),
+			})
+		end
 	end
 end
 
@@ -207,6 +221,20 @@ function stairs.register_slab(subname, recipeitem, groups, images, description,
 				{recipeitem, recipeitem, recipeitem},
 			},
 		})
+
+		-- Fuel
+		local baseburntime = minetest.get_craft_result({
+			method = "fuel",
+			width = 1,
+			items = {recipeitem}
+		}).time
+		if baseburntime > 0 then
+			minetest.register_craft({
+				type = "fuel",
+				recipe = 'stairs:slab_' .. subname,
+				burntime = math.floor(baseburntime * 0.5),
+			})
+		end
 	end
 end