Update sign help

mods/ITEMS/signs/init.lua

@@ -200,7 +200,7 @@ end)
 minetest.register_node("signs:sign_wall", {
 	description = "Sign",
 	_doc_items_longdesc = "Signs can be written and come in two variants: Wall sign and sign on a sign post. Signs can be placed on the top and the sides of other blocks, but not below them.",
-	_doc_items_usagehelp = "Place the sign at the side to build a wall sign, place it on top of another block to build a sign with a sign post. Rightclick the sign to edit its text.",
+	_doc_items_usagehelp = "Place the sign at the side to build a wall sign, place it on top of another block to build a sign with a sign post.\nAfter placing the sign, you can write something on it. You have 4 lines of text with up to 15 characters for each line; anything beyond these limits is lost. The text can not be changed once it has been written; you have to break and place the sign again.",
 	inventory_image = "default_sign.png",
 	walkable = false,
 	is_ground_content = false,