Added a demo mode to show or hide instance warnings that data is deleted

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

js/src/types/config.model.ts

@@ -3,6 +3,7 @@ export interface IConfig {
   description: string;
 
   registrationsOpen: boolean;
+  demoMode: boolean;
   countryCode: string;
   location: {
     latitude: number;