Enforce max bid to stop people ruining the demo (#86)

src/components/Modal.jsx

@@ -47,6 +47,7 @@ const ItemModal = () => {
   const { activeItem, openModal, closeModal } = useContext(ModalsContext);
   const [secondaryImageSrc, setSecondaryImageSrc] = useState("");
   const minIncrease = 1;
+  const maxIncrease = 10;
   const [bid, setBid] = useState();
   const [valid, setValid] = useState("");
   const [isSubmitting, setIsSubmitting] = useState("");
@@ -114,6 +115,13 @@ const ItemModal = () => {
       setIsSubmitting(false);
       return;
     }
+    // Ensure input is small enough
+    if (amount > status.amount + maxIncrease) {
+      setFeedback(`For the demo you can only increase the price up to ${activeItem.currency}${maxIncrease} per bid.`);
+      setValid("is-invalid");
+      setIsSubmitting(false);
+      return;
+    }
     // Finally, place bid
     updateDoc(doc(db, "auction", "items"), {
       [formatField(activeItem.id, status.bids + 1)]: {