Document converting a TileMap node to TileMapLayer using the editor

doc/classes/TileMap.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8" ?>
-<class name="TileMap" inherits="Node2D" deprecated="Use multiple [TileMapLayer] nodes instead." keywords="gridmap" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
+<class name="TileMap" inherits="Node2D" deprecated="Use multiple [TileMapLayer] nodes instead. To convert a TileMap to a set of TileMapLayer nodes, open the TileMap bottom panel with the node selected, click the toolbox icon in the top-right corner and choose &apos;Extract TileMap layers as individual TileMapLayer nodes&apos;." keywords="gridmap" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
 	<brief_description>
 		Node for 2D tile-based maps.
 	</brief_description>

scene/2d/tile_map.cpp

@@ -817,6 +817,8 @@ TypedArray<Vector2i> TileMap::get_surrounding_cells(const Vector2i &p_coords) {
 PackedStringArray TileMap::get_configuration_warnings() const {
 	PackedStringArray warnings = Node::get_configuration_warnings();
 
+	warnings.push_back(RTR("The TileMap node is deprecated as it is superseded by the use of multiple TileMapLayer nodes.\nTo convert a TileMap to a set of TileMapLayer nodes, open the TileMap bottom panel with this node selected, click the toolbox icon in the top-right corner and choose \"Extract TileMap layers as individual TileMapLayer nodes\"."));
+
 	// Retrieve the set of Z index values with a Y-sorted layer.
 	RBSet<int> y_sorted_z_index;
 	for (const TileMapLayer *layer : layers) {