added "docs/en" directory and moved

doc/en/example/costlysetup/conftest.py

@@ -0,0 +1,17 @@
+
+def pytest_funcarg__setup(request):
+    return request.cached_setup(
+        setup=lambda: CostlySetup(),
+        teardown=lambda costlysetup: costlysetup.finalize(),
+        scope="session",
+    )
+
+class CostlySetup:
+    def __init__(self):
+        import time
+        print ("performing costly setup")
+        time.sleep(5)
+        self.timecostly = 1
+
+    def finalize(self):
+        del self.timecostly