Docs: Adding memory requirements to image renderer docs (#95571)

Adding memory requirements to image renderer docs

docs/sources/setup-grafana/image-rendering/_index.md

@@ -40,6 +40,12 @@ All PhantomJS support has been removed. Instead, use the Grafana Image Renderer
 
 To install the plugin, refer to the [Grafana Image Renderer Installation instructions](/grafana/plugins/grafana-image-renderer/?tab=installation#installation).
 
+### Memory requirements
+
+Rendering images requires a lot of memory, mainly because Grafana creates browser instances in the background for the actual rendering. Grafana recommends a minimum of 16GB of free memory on the system rendering images.
+
+Rendering multiple images in parallel requires an even bigger memory footprint. You can use the remote rendering service in order to render images on a remote system, so your local system resources are not affected.
+
 ## Configuration
 
 The Grafana Image Renderer plugin has a number of configuration options that are used in plugin or remote rendering modes.