Update app/.htmlvalidate.json

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: DinneK

app/.htmlvalidate.json

@@ -1,7 +1,7 @@
 {
-    "extends": ["html-validate:recommended"],
-    "rules": {
-        "void-style": "off",
-        "no-trailing-whitespace": "off"
-    }
-}
+  "extends": ["html-validate:recommended"],
+  "rules": {
+    "void-style": "off",
+    "no-trailing-whitespace": "off"
+  }
+}