Document BROWSER=wslview for open_in_browser under WSL (#7965)

scrapy/utils/response.py

@@ -90,6 +90,10 @@ def open_in_browser(
         def parse_details(self, response):
             if "item name" not in response.text:
                 open_in_browser(response)
+
+    On the Windows Subsystem for Linux, set the ``BROWSER`` environment
+    variable to `wslview <https://github.com/wslutilities/wslu>`_ to open the
+    response in a Windows browser, which cannot read Linux paths otherwise.
     """
     # circular imports
     from scrapy.http import HtmlResponse, TextResponse  # noqa: PLC0415