update files inside importify folder

public/vendor/maennchen/zipstream-php/guides/Varnish.rst

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+Usage with Varnish
+=============
+
+Serving a big zip with varnish in between can cause random stream close.
+This can be solved by adding attached code to the vcl file.
+
+To avoid the problem, add the following to your varnish config file:
+
+.. code-block::
+    sub vcl_recv {
+        # Varnish can’t intercept the discussion anymore
+        # helps for streaming big zips
+        if (req.url ~ "\.(tar|gz|zip|7z|exe)$") {
+            return (pipe);
+        }
+    }
+    # Varnish can’t intercept the discussion anymore
+    # helps for streaming big zips
+    sub vcl_pipe {
+        set bereq.http.connection = "close";
+        return (pipe);
+    }