Add preset argument to webp_options processing option

Author: DarthSim

docs/usage/processing.mdx

@@ -815,8 +815,8 @@ Allows redefining PNG saving options. All arguments have the same meaning as wit
 ### WebP options ((pro)) {#webp-options}
 
 ```imgproxy_url_option
-webp_options:%compression:%smart_subsample
-webpo:%compression:%smart_subsample
+webp_options:%compression:%smart_subsample:%preset
+webpo:%compression:%smart_subsample:%preset
 ```
 
 Allows redefining WebP saving options. All arguments have the same meaning as with the [Advanced WebP compression](../configuration/options.mdx#advanced-webp-compression) configs. All arguments are optional and can be omitted.