feat(user email setting): added field to save user email

fix #122

server/interfaces/api/userSettingsInterfaces.ts

@@ -2,6 +2,7 @@ import { NotificationAgentKey } from '../../lib/settings';
 
 export interface UserSettingsGeneralResponse {
   username?: string;
+  email?: string;
   discordId?: string;
   locale?: string;
   region?: string;