Adding JsonConverter benchmark

src/JsonConverterBench.php

@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\Csv;
+
+use PhpBench\Attributes as Bench;
+
+final class JsonConverterBench
+{
+    #[Bench\OutputTimeUnit('seconds')]
+    #[Bench\Assert('mode(variant.mem.peak) < 2097152'), Bench\Assert('mode(variant.time.avg) < 10000000')]
+    public function benchConverting10000CSVRowsUsingJsonConverter(): void
+    {
+        $document = Reader::createFromPath(dirname(__DIR__).'/test_files/prenoms.csv');
+        $document->setHeaderOffset(0);
+        $document->setDelimiter(';');
+        CharsetConverter::addTo($document, 'iso-8859-15', 'utf-8');
+
+        $bytes = JsonConverter::create()->save($document, ($tmpFile = tmpfile()));
+
+        assert($bytes === filesize(stream_get_meta_data($tmpFile)['uri']));
+    }
+
+    #[Bench\OutputTimeUnit('seconds')]
+    #[Bench\Assert('mode(variant.mem.peak) <= 7641688'), Bench\Assert('mode(variant.time.avg) < 10000000')]
+    public function benchConverting10000CSVRowsUsingJsonEncode(): void
+    {
+        $document = Reader::createFromPath(dirname(__DIR__).'/test_files/prenoms.csv');
+        $document->setHeaderOffset(0);
+        $document->setDelimiter(';');
+        CharsetConverter::addTo($document, 'iso-8859-15', 'utf-8');
+
+        $tmpFile = tmpfile();
+        $filename = stream_get_meta_data($tmpFile)['uri'];
+
+        $bytes = file_put_contents($filename, json_encode($document));
+
+        assert($bytes === filesize($filename));
+    }
+}