Add reference page for createMiddleware (#1025)

Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>

Author: amirhhashemi

src/routes/solid-start/reference/server/create-middleware.mdx

@@ -0,0 +1,51 @@
+---
+title: createMiddleware
+---
+
+`createMiddleware` creates a configuration object for SolidStart that specifies when middleware functions are executed during the request lifecycle.
+
+There are two lifecycle events available: `onRequest` and `onBeforeResponse`.
+
+- The `onRequest` event is triggered at the beginning of the request lifecycle, before the request is handled by the route handler.
+- The `onBeforeResponse` event is triggered after a request has been processed by the route handler but before the response is sent to the client.
+
+<Callout type="info" title="Note">
+
+SolidStart will only execute the middleware functions if the path to the middleware file is configured within `app.config.ts` using the `middleware` option.
+This file must export the configuration using `export default`.
+
+</Callout>
+
+Learn more about middleware in the [Middleware documentation](/solid-start/advanced/middleware).
+
+## Parameters
+
+`createMiddleware` takes an object with the following keys:
+
+- `onRequest` (optional): A middleware function or an array of functions to execute at the `onRequest` event.
+  If an array is provided, the middleware functions will be executed one by one, in the order they appear in the array.
+- `onBeforeResponse` (optional): A middleware function or an array of functions to execute at the `onBeforeResponse` event.
+  If an array is provided, the middleware functions will be executed one by one, in the order they appear in the array.
+
+## Example
+
+```ts title="src/middleware/index.ts"
+import { createMiddleware } from "@solidjs/start/middleware";
+
+export default createMiddleware({
+	onRequest: (event) => {
+		console.log("Request received:", event.request.url);
+	},
+	onBeforeResponse: (event) => {
+		console.log("Sending response:", event.response.status);
+	},
+});
+```
+
+```ts title="app.config.ts"
+import { defineConfig } from "@solidjs/start/config";
+
+export default defineConfig({
+	middleware: "src/middleware/index.ts",
+});
+```

src/routes/solid-start/reference/server/data.json

@@ -7,6 +7,7 @@
 		"http-status-code.mdx",
 		"start-server.mdx",
 		"create-handler.mdx",
-		"get-server-function-meta.mdx"
+		"get-server-function-meta.mdx",
+		"create-middleware.mdx"
 	]
-}
+}