Add MySQL migrations

Author: TheIndra55

.env.example

@@ -1,3 +1,5 @@
 DB_DSN=mysql:host=localhost;dbname=shika
 DB_USERNAME=
 DB_PASSWORD=
+
+MAXMIND_PATH=

migrations/mysql/0004_extend_visits.php

@@ -0,0 +1,15 @@
+<?php
+
+use Astylodon\Migrations\Database\DatabaseInterface;
+use Astylodon\Migrations\Migration;
+
+return new class implements Migration
+{
+    public function up(DatabaseInterface $database)
+    {
+        $database->exec("ALTER TABLE visits ADD country_code VARCHAR(2)");
+        $database->exec("ALTER TABLE visits ADD browser VARCHAR(50)");
+        $database->exec("ALTER TABLE visits ADD operating_system VARCHAR(50)");
+        $database->exec("ALTER TABLE visits ADD device_type VARCHAR(8)");
+    }
+};