Explicitly type simple array

Add typings for the pattern: `let x = []` which defaults to `let x: any[] = []`

#60565

src/vs/workbench/api/electron-browser/mainThreadComments.ts

@@ -151,7 +151,7 @@ export class MainThreadComments extends Disposable implements MainThreadComments
 	}
 
 	getVisibleEditors(): ICodeEditor[] {
-		let ret = [];
+		let ret: ICodeEditor[] = [];
 
 		this._editorService.visibleControls.forEach(control => {
 			if (isCodeEditor(control.getControl())) {