dummy output: add readme

Author: Lukas955

src/plugins/output/dummy/README.rst

@@ -0,0 +1,25 @@
+Dummy (output plugin)
+=====================
+
+The plugin provides a means to test the collector without actually storing any data.
+Every processing of an IPFIX packet can have specified delay so that throughput of
+the collector can be tested and required performance of output plugins can be determined.
+
+Example configuration
+---------------------
+
+.. code-block:: xml
+
+    <output>
+        <name>Dummy output</name>
+        <plugin>dummy</plugin>
+        <params>
+            <delay>0</delay>
+        </params>
+    </output>
+
+Parameters
+----------
+
+:``delay``:
+    Minimum delay between processing of two consecutive messages in microseconds.