core: contest: add feature whitelist for hidden contest fule

packages/hydrooj/src/interface.ts

@@ -422,10 +422,13 @@ export interface ScoreboardConfig {
     lockAt?: Date;
 }
 
+export type Feature = 'scoreboard' | 'download';
+
 export interface ContestRule<T = any> {
     _originalRule?: Partial<ContestRule<T>>;
     TEXT: string;
     hidden?: boolean;
+    features?: Feature[];
     check: (args: any) => any;
     statusSort: Record<string, 1 | -1>;
     submitAfterAccept: boolean;