Add webmin documentation (#30617)

* Add webmin documentation

* List all currently provided sensors

* Update source/_integrations/webmin.markdown

Co-authored-by: Klaas Schoute <klaas_schoute@hotmail.com>

---------

Co-authored-by: Klaas Schoute <klaas_schoute@hotmail.com>

source/_integrations/webmin.markdown

@@ -0,0 +1,35 @@
+---
+title: Webmin
+description: Instructions on how to set up Webmin with Home Assistant.
+ha_category:
+  - System monitor
+ha_release: 2024.3
+ha_iot_class: Local Polling
+ha_config_flow: true
+ha_codeowners:
+  - '@autinerd'
+ha_domain: webmin
+ha_integration_type: integration
+ha_platforms:
+  - sensor
+---
+
+[Webmin](https://webmin.com) is a web-based interface for the system administration of Unix-like servers.
+
+This {% term integration %} provides sensors for monitoring the CPU and memory usage of your server.
+
+{% include integrations/config_flow.md %}
+
+## Sensors
+
+**All entities are disabled by default, you need to enable the entities that you wish to use.**
+
+Following sensors will be added:
+
+- Load (1m)
+- Load (5m)
+- Load (15m)
+- Memory total
+- Memory free
+- Swap total
+- Swap free