detect and add mt5.0 coral reefs

mapgen.lua

@@ -1113,3 +1113,61 @@ if minetest.get_modpath("fireflies") then
 		decoration = "fireflies:hidden_firefly",
 	})
 end
+
+-- Coral Reef (Minetest 5.0)
+if minetest.registered_nodes["default:coral_green"] then
+	minetest.register_decoration({
+		name = "default:corals",
+		deco_type = "simple",
+		place_on = {"default:sand"},
+		place_offset_y = -1,
+		sidelen = 4,
+		noise_params = {
+			offset = -4,
+			scale = 4,
+			spread = {x = 50, y = 50, z = 50},
+			seed = 7013,
+			octaves = 3,
+			persist = 0.7,
+		},
+		biomes = {
+			"desert_ocean",
+			"savanna_ocean",
+			"junglee_ocean",
+		},
+		y_max = -2,
+		y_min = -8,
+		flags = "force_placement",
+		decoration = {
+			"default:coral_green", "default:coral_pink",
+			"default:coral_cyan", "default:coral_brown",
+			"default:coral_orange", "default:coral_skeleton",
+		},
+	})
+
+	-- Kelp
+
+	minetest.register_decoration({
+		name = "default:kelp",
+		deco_type = "simple",
+		place_on = {"default:sand"},
+		place_offset_y = -1,
+		sidelen = 16,
+		noise_params = {
+			offset = -0.04,
+			scale = 0.1,
+			spread = {x = 200, y = 200, z = 200},
+			seed = 87112,
+			octaves = 3,
+			persist = 0.7
+		},
+		biomes = {
+			"frost_ocean", "grassy_ocean", "sandstone_ocean", "swamp_ocean"},
+		y_max = -5,
+		y_min = -10,
+		flags = "force_placement",
+		decoration = "default:sand_with_kelp",
+		param2 = 48,
+		param2_max = 96,
+	})
+end