Add heading

Author: schweetheart

website/src/pages/plugins/presets/preset-client.mdx

@@ -491,6 +491,8 @@ console.log(response.status)
 console.log(await response.json())
 ```
 
+### Hashing algorithm
+
 To override the default hash algorithm of sha1 set `persistedDocuments.hashAlgorithm`
 
 ```ts filename="codegen.ts" {10-12}