Allow caching CORS responses.

hc/api/decorators.py

@@ -109,6 +109,7 @@ def cors(*methods):
             response["Access-Control-Allow-Origin"] = "*"
             response["Access-Control-Allow-Headers"] = "X-Api-Key"
             response["Access-Control-Allow-Methods"] = methods_str
+            response["Access-Control-Max-Age"] = "600"
             return response
 
         return wrapper