Add composer dependencies

composer.json

+{
+    "name": "drupal/subrequests",
+    "description": "Add a front controller that you can use to make subrequests.",
+    "type": "drupal-module",
+    "require": {
+        "php-jsonpointer/php-jsonpointer": "^3.0"
+    },
+    "license": "GPL-2.0+",
+    "authors": [
+        {
+            "name": "Mateu Aguiló Bosch",
+            "email": "mateu.aguilo.bosch@gmail.com"
+        }
+    ],
+    "minimum-stability": "dev"
+}