[gtk/test-coverage: 4/8] node-editor: Make the help more helpful

[Matthias Clasen <matthiasc src gnome org>]

commit 69336fa5f182b4ede201e0553afc9444c88f00d8
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Jul 15 07:42:35 2022 -0400

    node-editor: Make the help more helpful
    
    I struggled to remember how newlines vs strings work in
    this format, so put it in the docs.

 demos/node-editor/node-format.md | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/demos/node-editor/node-format.md b/demos/node-editor/node-format.md
index cc457f1a20..9664090274 100644
--- a/demos/node-editor/node-format.md
+++ b/demos/node-editor/node-format.md
@@ -13,6 +13,8 @@ Each node has its own `<node-name>` and supports a custom set of properties, eac
 
 When serializing and the value of a property equals the default value, this value will not be serialized. 
Serialization aims to produce an output as small as possible.
 
+To embed newlines in strings, use \A. To break a long string into multiple lines, escape the newline with a 
\.
+
 # Nodes
 
 ### container