mark a few interface properties readonly

src/vs/editor/contrib/suggest/suggestModel.ts

@@ -19,22 +19,22 @@ import { CursorChangeReason, ICursorSelectionChangedEvent } from 'vs/editor/comm
 import { ICodeEditor } from 'vs/editor/browser/editorBrowser';
 
 export interface ICancelEvent {
-	retrigger: boolean;
+	readonly retrigger: boolean;
 }
 
 export interface ITriggerEvent {
-	auto: boolean;
+	readonly auto: boolean;
 }
 
 export interface ISuggestEvent {
-	completionModel: CompletionModel;
-	isFrozen: boolean;
-	auto: boolean;
+	readonly completionModel: CompletionModel;
+	readonly isFrozen: boolean;
+	readonly auto: boolean;
 }
 
 export interface SuggestTriggerContext {
-	auto: boolean;
-	triggerCharacter?: string;
+	readonly auto: boolean;
+	readonly triggerCharacter?: string;
 }
 
 export class LineContext {