feat: stable logger (#13907)

Co-authored-by: Armand Philippot <git@armand.philippot.eu>

Author: ematipico

astro.sidebar.ts

@@ -148,6 +148,7 @@ export const sidebar = [
 					'reference/dev-toolbar-app-reference',
 					'reference/session-driver-reference',
 					'reference/font-provider-reference',
+					'reference/logger-reference',
 					'reference/container-reference',
 					'reference/programmatic-reference',
 				],
@@ -161,7 +162,6 @@ export const sidebar = [
 					'reference/experimental-flags/chrome-devtools-workspace',
 					'reference/experimental-flags/svg-optimization',
 					'reference/experimental-flags/advanced-routing',
-					'reference/experimental-flags/logger',
 				],
 			}),
 			'reference/legacy-flags',

src/content/docs/en/reference/api-reference.mdx

@@ -1229,3 +1229,55 @@ content="
   "
 >
 ```
+### `logger`
+
+<p>
+
+  **Type**: `object | undefined`
+  <Since v="6.4.0" />
+</p>
+
+An object that allows you to add additional logs during the rendering of a page. This is particularly useful with [on-demand routes](/en/guides/on-demand-rendering/) and when connecting log aggregation services (e.g. Kibana, Grafana, Loki).
+#### `logger.error()`
+<p>
+
+  **Type**: `(msg: string) => void`
+  <Since v="6.4.0" />
+</p>
+
+Emits a message with `error` level.
+
+```astro title="src/pages/index.astro"
+---
+Astro.logger.error("Can't find the checkout ID.");
+---
+```
+  
+#### `logger.warn()`
+<p>
+
+  **Type**: `(msg: string) => void`
+  <Since v="6.4.0" />
+</p>
+Emits a message with `warn` level.
+
+```astro title="src/pages/index.astro"
+---
+Astro.logger.warn("Can't find the checkout ID.");
+---
+```  
+  
+#### `logger.info()`
+<p>
+
+  **Type**: `(msg: string) => void`
+  <Since v="6.4.0" />
+</p>
+  
+Emits a message with `info` level.
+
+```astro title="src/pages/index.astro"
+---
+Astro.logger.info("Can't find the checkout ID.");
+---
+```