Support selectionForeground in dom

Part of #3810

src/browser/services/Services.ts

@@ -101,6 +101,7 @@ export interface ISelectionService {
   shouldForceSelection(event: MouseEvent): boolean;
   refresh(isLinuxMouseSelection?: boolean): void;
   onMouseDown(event: MouseEvent): void;
+  isCellInSelection(x: number, y: number): boolean;
 }
 
 export const ISoundService = createDecorator<ISoundService>('SoundService');