multi-root folders: excluding dot files from a folder makes it invisible in...

multi-root folders: excluding dot files from a folder makes it invisible in file explorer (fixes #37899)

src/vs/workbench/parts/files/browser/views/explorerViewer.ts

@@ -709,7 +709,7 @@ export class FileFilter implements IFilter {
 	}
 
 	private doIsVisible(stat: FileStat): boolean {
-		if (stat instanceof NewStatPlaceholder) {
+		if (stat instanceof NewStatPlaceholder || stat.isRoot) {
 			return true; // always visible
 		}