Added doc for Gaussian Blur in Image Editor (#3046)

---------

Co-authored-by: Adrien Dupuis <61695653+adriendupuis@users.noreply.github.com>

Author: mnocon

code_samples/back_office/image_editor/config/packages/image_editor.yaml

@@ -38,3 +38,4 @@ ibexa:
                                 id: dot
                                 priority: 50
                 image_quality: 0.8
+                gaussian_blur_strength: 0.05

docs/content_management/images/configure_image_editor.md

@@ -33,7 +33,9 @@ The following example sets the aspect ratio values and label names for buttons u
 [[= include_file('code_samples/back_office/image_editor/config/packages/image_editor.yaml', 0, 36) =]]
 ```
 
-### Image quality
+### Image file size optimization
+
+#### Image quality
 
 You can configure the quality of the images modified in the Image Editor with the following configuration.
 
@@ -44,6 +46,20 @@ The default quality is 0.92:
 [[= include_file('code_samples/back_office/image_editor/config/packages/image_editor.yaml', 0, 4) =]] [[= include_file('code_samples/back_office/image_editor/config/packages/image_editor.yaml', 39, 40) =]]
 ```
 
+#### Gaussian blur strength
+
+You can configure the gaussian blur strength applied during image optimization with the following configuration.
+
+``` yaml
+[[= include_file('code_samples/back_office/image_editor/config/packages/image_editor.yaml', 0, 4) =]] [[= include_file('code_samples/back_office/image_editor/config/packages/image_editor.yaml', 40, 41) =]]
+```
+
+The setting accepts float values between 0 and 10.0, where higher values increase blur and reduce file size, while lower values maintain sharpness.
+The default value is 0.05.
+
+Processing large images with high blur values (above 5) can be time-consuming and may result in request timeouts.
+Keep this in mind when configuring blur strength for environments that handle high-resolution images, and adjust [PHP's `max_execution_time`](https://www.php.net/manual/en/info.configuration.php#ini.max-execution-time) if needed.
+
 ### Additional information
 
 Each image can be accompanied by additional information that isn't visible to the user.