Information about rel_file support in editorUrl

Covers changes from phpstan/phpstan-src#1414

website/src/user-guide/output-format.md

@@ -57,4 +57,12 @@ parameters:
 	editorUrl: 'phpstorm://open?file=%%file%%&line=%%line%%'
 ```
 
+<div class="bg-blue-100 border-l-4 border-blue-500 text-blue-700 p-4 mb-4" role="alert">
+
+**Support for analysis executed in virtual environment**
+
+If you run PHPStan analysis within Docker container (or using other virtualisation tool) you may need to use `%rel_file%` instead of `%file%`. This will use file's path relative to your project's directory. In the end your `editorUrl` should have value like this: `phpstorm://open?file=/path/to/your/project/%%rel_file%%&line=%%line%%`.
+
+</div>
+
 To make the text really clickable in your terminal you might need to register the protocol in your system; see [eclemens/atom-url-handler](https://github.com/eclemens/atom-url-handler) for an example.