Make it clear we're checking the filename

Replaces `file[0]` with a more meaningful `filename`.

Author: elenatanasoiu

extensions/ql-vscode/src/skeleton-query-wizard.ts

@@ -184,7 +184,9 @@ export class SkeletonQueryWizard {
 
     const folderUri = Uri.file(join(this.storagePath, folderName));
     const files = await workspace.fs.readDirectory(folderUri);
-    const qlFiles = files.filter((file) => file[0].endsWith(".ql"));
+    const qlFiles = files.filter(([filename, _fileType]) =>
+      filename.endsWith(".ql"),
+    );
 
     return `example${qlFiles.length + 1}.ql`;
   }