benchmark: include ascii to fs/readfile

PR-URL: nodejs#54988
Reviewed-By: Daniel Lemire <daniel@lemire.me>
Reviewed-By: Raz Luvaton <rluvaton@gmail.com>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Chemi Atlow <chemi@atlow.co.il>

benchmark/fs/readFileSync.js

@@ -4,7 +4,7 @@ const common = require('../common.js');
 const fs = require('fs');
 
 const bench = common.createBenchmark(main, {
-  encoding: ['undefined', 'utf8'],
+  encoding: ['undefined', 'utf8', 'ascii'],
   path: ['existing', 'non-existing'],
   hasFileDescriptor: ['true', 'false'],
   n: [1e4],

benchmark/fs/readfile.js

@@ -12,7 +12,7 @@ const filename = tmpdir.resolve(`.removeme-benchmark-garbage-${process.pid}`);
 
 const bench = common.createBenchmark(main, {
   duration: [5],
-  encoding: ['', 'utf-8'],
+  encoding: ['', 'utf-8', 'ascii'],
   len: [1024, 16 * 1024 * 1024],
   concurrent: [1, 10],
 });