Add webhook verification functionality for secure payload validation

Author: jnsdls

.changeset/webhook-verification.md

@@ -0,0 +1,22 @@
+---
+"thirdweb": minor
+---
+
+Added webhook verification functionality to securely verify incoming webhooks from thirdweb. This includes:
+
+- New `Webhook.parse` function to verify webhook signatures and timestamps
+- Support for both `x-payload-signature` and `x-pay-signature` header formats
+- Timestamp verification with configurable tolerance
+- Version 2 webhook payload type support
+
+Example usage:
+```typescript
+import { Webhook } from "thirdweb/bridge";
+
+const webhook = await Webhook.parse(
+  payload,
+  headers,
+  secret,
+  300 // optional tolerance in seconds
+);
+```