chore: add nullout to docs

Signed-off-by: Bence Csati <[email protected]>

Author: csatib02

content/docs/configuration/plugins/outputs/null.md

@@ -0,0 +1,25 @@
+---
+title: Null
+weight: 200
+generated_file: true
+---
+
+# Null output plugin for Fluentd
+## Overview
+
+For details, see [https://docs.fluentd.org/output/null](https://docs.fluentd.org/output/null).
+
+## Example output configurations
+
+```yaml
+spec:
+  nullout:
+    never_flush: false
+```
+
+## Configuration
+## NullOutputConfig
+
+### never_flush (*bool, optional) {#nulloutputconfig-never_flush}
+
+The parameter for testing to simulate the output plugin that never succeeds to flush.