re-add composer

extension/composer.json

+{
+  "require": {
+    "phpoffice/phpspreadsheet": "^1.3",
+    "ext-json": "*",
+    "typo3/cms-core": "^8.7"
+  },
+  "require-dev": {
+    "phpunit/phpunit": "^6.5"
+  },
+  "autoload": {
+    "psr-4": {
+      "qfq\\": ["qfq/",
+        "Source/api/",
+        "Source/external/",
+        "Source/core/",
+        "Source/core/database/",
+        "Source/core/exceptions/",
+        "Source/core/form/",
+        "Source/core/helper/",
+        "Source/core/report/",
+        "Source/core/store/",
+        "Source/core/typo3/"]
+    }
+  }
+}