doc: add example and explanation for retryInterval in pipeline tuning…

… page

Signed-off-by: Quentin Faidide <[email protected]>

docs/user-guide/reference/pipeline-tuning.md

@@ -7,6 +7,7 @@ processing cycle.
 - `readBatchSize` - How many messages to read for each cycle, defaults to `500`.
 - `bufferMaxLength` - How many unprocessed messages can be existing in the Inter-Step Buffer, defaults to `30000`.
 - `bufferUsageLimit` - The percentage of the buffer usage limit, a valid number should be less than 100. Default value is `80`, which means `80%`.
+- `retryInterval` - The time to wait before retrying after a failure of the UDF or of the ISBSVC.
 
 These parameters can be customized under `spec.limits` as below, once defined, they apply to all the vertices and Inter-Step Buffers of the pipeline.
 
@@ -20,6 +21,7 @@ spec:
     readBatchSize: 100
     bufferMaxLength: 30000
     bufferUsageLimit: 85
+    retryInterval: 0.05s
 ```
 
 They also can be defined in a vertex level, which will override the pipeline level settings.
@@ -34,6 +36,7 @@ spec:
     readBatchSize: 100
     bufferMaxLength: 30000
     bufferUsageLimit: 85
+    retryInterval: 0.05s
   vertices:
     - name: in
       source: