Add note about base 64 encoded event body (redwoodjs#9595)

Co-authored-by: Daniel Choudhury <[email protected]>

docs/docs/webhooks.md

@@ -214,6 +214,14 @@ This is a variation on the SHA256 HMAC verification that works with binary buffe
 
 Svix (and by extension, Clerk) gives you a secret token that it uses to create a hash signature with each payload. This hash signature is included with the headers of each request as `svix-signature`.
 
+> Some production environments, like Vercel, might base64 encode the request body string. In that case, the body must be conditionally parsed.
+> ```js
+> export const handler = async (event: APIGatewayEvent) => {
+>   const body = event.isBase64Encoded
+>     ? Buffer.from(event.body, 'base64').toString('utf-8')
+>     : event.body
+> ```
+
 ```tsx
 import type { APIGatewayEvent } from 'aws-lambda'
 import {