Add dockerfile and update config file

SIG_spbu/config.php

@@ -0,0 +1,11 @@
+<?php
+define('DB_HOST', getenv('DB_HOST'));
+define('DB_USER', getenv('DB_USER'));
+define('DB_PASS', getenv('DB_PASS'));
+define('DB_NAME', getenv('DB_NAME'));
+
+$conn = new mysqli(DB_HOST, DB_USER, DB_PASS, DB_NAME);
+if ($conn->connect_error) {
+    die("Koneksi gagal: " . $conn->connect_error);
+}
+?>