Use readonly for hover options as they should not be touched

Fixes microsoft#189187

Author: Tyriar

src/vs/workbench/services/hover/browser/hover.ts

@@ -30,7 +30,7 @@ export interface IHoverService {
 	 * });
 	 * ```
 	 */
-	showHover(options: IHoverOptions, focus?: boolean): IHoverWidget | undefined;
+	showHover(options: Readonly<IHoverOptions>, focus?: boolean): IHoverWidget | undefined;
 
 	/**
 	 * Hides the hover if it was visible. This call will be ignored if the the hover is currently

src/vs/workbench/services/hover/browser/hoverService.ts

@@ -36,7 +36,7 @@ export class HoverService implements IHoverService {
 		contextMenuService.onDidShowContextMenu(() => this.hideHover());
 	}
 
-	showHover(options: IHoverOptions, focus?: boolean): IHoverWidget | undefined {
+	showHover(options: Readonly<IHoverOptions>, focus?: boolean): IHoverWidget | undefined {
 		if (getHoverOptionsIdentity(this._currentHoverOptions) === getHoverOptionsIdentity(options)) {
 			return undefined;
 		}