docs(solid-start): serialization adapters

Author: m9tdev

docs/start/framework/solid/guide/server-functions.md

@@ -7,3 +7,28 @@ replace:
     '@tanstack/react-router': '@tanstack/solid-router',
   }
 ---
+
+### Custom serialization adapters
+
+You can create custom serialization adapters to handle complex types that can't be serialized by default.
+
+Example:
+
+```ts
+// src/start.ts
+import { createStart } from '@tanstack/solid-start'
+import { createSerializationAdapter } from '@tanstack/solid-router'
+
+const bigIntAdapter = createSerializationAdapter({
+  key: 'bigint',
+  test: (value: unknown): value is bigint => typeof value === 'bigint',
+  toSerializable: (bigInt) => bigInt.toString(),
+  fromSerializable: (value) => BigInt(value),
+})
+
+export const startInstance = createStart(() => {
+  return {
+    serializationAdapters: [bigIntAdapter],
+  }
+})
+```