Update for Vulkan-Docs 1.3.226

registry/reg.py

@@ -996,6 +996,11 @@ class Registry:
 
                 # Determine the required extension or version needed for a require block
                 # Assumes that only one of these is specified
+                # 'extension', and therefore 'required_key', may be a boolean
+                # expression of extension names.
+                # 'required_key' is used only as a dictionary key at
+                # present, and passed through to the script generators, so
+                # they must be prepared to parse that expression.
                 required_key = require.get('feature')
                 if required_key is None:
                     required_key = require.get('extension')