minor #13687 Link to the NGINX Unit article for Symfony apps (javiereguiluz)

This PR was squashed before being merged into the 3.4 branch.

Discussion
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Link to the NGINX Unit article for Symfony apps

Fixes #13596.

Commits
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9787811 Link to the NGINX Unit article for Symfony apps

Author: javiereguiluz

setup/web_server_configuration.rst

@@ -313,6 +313,11 @@ The **minimum configuration** to get your application running under nginx is:
         access_log /var/log/nginx/project_access.log;
     }
 
+.. tip::
+
+    If you use NGINX Unit, check out the official article about
+    `How to run Symfony applications using NGINX Unit`_.
+
 .. note::
 
     Depending on your PHP-FPM config, the ``fastcgi_pass`` can also be
@@ -344,3 +349,4 @@ For advanced nginx configuration options, read the official `nginx documentation
 .. _`Apache documentation`: https://httpd.apache.org/docs/
 .. _`FastCgiExternalServer`: https://docs.oracle.com/cd/B31017_01/web.1013/q20204/mod_fastcgi.html#FastCgiExternalServer
 .. _`nginx documentation`: https://www.nginx.com/resources/wiki/start/topics/recipes/symfony/
+.. _`How to run Symfony applications using NGINX Unit`: https://unit.nginx.org/howto/symfony/