by Primsi: add composer file.

composer.json

+{
+  "name": "drupal/commerce_datatrans",
+  "type": "drupal-module",
+  "description": "Datatrans gateway for commerce 8.x-2.x",
+  "keywords": ["Drupal"],
+  "license": "GPL-2.0+",
+  "homepage": "https://www.drupal.org/project/commerce_datatrans",
+  "support": {
+    "issues": "https://www.drupal.org/project/issues/commerce_datatrans",
+    "source": "http://cgit.drupalcode.org/commerce_datatrans"
+  },
+  "require": {
+    "drupal/commerce": "2.*"
+  }
+}