restore composer.json, add mysqli extension

tests/Unit/ExampleTest.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace Tests\Unit;
+
+use PHPUnit\Framework\TestCase;
+
+class ExampleTest extends TestCase
+{
+    /**
+     * A basic test example.
+     */
+    public function test_that_true_is_true(): void
+    {
+        $this->assertTrue(true);
+    }
+}