Issue #3497781: Add an XB recipe that is part of the project template

.ddev/homeadditions/bin/generate-composer-json

@@ -10,10 +10,27 @@ $read_json = function (string $file): array {
   return json_decode($data, TRUE, flags: JSON_THROW_ON_ERROR);
 };
 
-$data = array_merge_recursive(
-  $read_json('project_template/composer.json'),
-  $read_json('dev.composer.json'),
-);
+// From \Drupal\Component\Utility\NestedArray::mergeDeep().
+$merge_deep = function (array ...$arrays) use (&$merge_deep): array {
+  $result = [];
+  foreach ($arrays as $array) {
+    foreach ($array as $key => $value) {
+      // Recurse when both values are arrays.
+      if (isset($result[$key]) && is_array($result[$key]) && is_array($value)) {
+        $result[$key] = $merge_deep($result[$key], $value);
+      }
+      // Otherwise, use the latter value, overriding any previous value.
+      else {
+        $result[$key] = $value;
+      }
+    }
+  }
+  return $result;
+};
+
+$base = $read_json('project_template/composer.json');
+$dev = $read_json('dev.composer.json');
+$data = $merge_deep($base, $dev);
 
 // If in a CI environment, make all path repository URLs absolute.
 if (getenv('CI') || getenv('TUGBOAT_PREVIEW')) {