docs: document dispute fees

clients/apps/web/src/app/(main)/docs/(mdx)/fees/page.mdx

@@ -57,6 +57,12 @@ which point we'll eventually need to trigger a payout on your behalf._
 
 - 10% on amount transferred
 
+## Dispute fees
+
+In some circumstances, customers can open a **dispute** to their bank if they don't recognize the payment that has been made. In this case, our payment processor immediately withdraws funds and bills us dispute fees. Those fees are not refunded, even if the dispute is won in our favor. That's why we pass on this fee.
+
+This fee is usually around **$15** per dispute.
+
 ## Custom pricing
 
 Large or fast-growing business? Or selling products cheaper than $10 with high