Added trace peer forwarder doc (opensearch-project#2245)

* Added trace peer forwarder doc

Signed-off-by: Asif Sohail Mohammed <[email protected]>

data-prepper-plugins/trace-peer-forwarder-processor/README.md

@@ -0,0 +1,43 @@
+# Trace Peer Forwarder Processor
+
+This processor is used to reduce the number of Events that will be forwarded in a Trace Analytics pipeline by half when using [Peer Forwarder](https://github.com/opensearch-project/data-prepper/blob/main/docs/peer_forwarder.md). 
+It groups the events based on `trace_id` similar to `service_map_stateful` and `otel_trace_raw ` processors. 
+
+In [Trace Analytics pipeline](https://github.com/opensearch-project/data-prepper/blob/main/docs/trace_analytics.md#trace-analytics-pipeline) each event is duplicated, when it is sent from `otel-trace-pipeline` to `raw-pipeline` and `service-map-pipeline`.
+So, the event will be forwarded once in each pipeline. Using this processor event will be forwarded only once in `otel-trace-pipeline` to correct peer. 
+
+## Basic Usage
+To get started with trace peer forwarder, create the following `pipeline.yaml` along with [Peer Forwarder](https://github.com/opensearch-project/data-prepper/blob/main/docs/peer_forwarder.md) in `data-prepper-config.yaml`
+
+```yaml
+otel-trace-pipeline:
+  delay: "100"
+  source:
+    otel_trace_source:
+  processor:
+    - trace_peer_forwarder:
+  sink:
+    - pipeline:
+        name: "raw-pipeline"
+    - pipeline:
+        name: "service-map-pipeline"
+raw-pipeline:
+  source:
+    pipeline:
+      name: "entry-pipeline"
+  processor:
+    - otel_trace_raw:
+  sink:
+    - opensearch:
+service-map-pipeline:
+  delay: "100"
+  source:
+    pipeline:
+      name: "entry-pipeline"
+  processor:
+    - service_map_stateful:
+  sink:
+    - opensearch:
+```
+
+In the above pipeline, events will be forwarded in the `otel-trace-pipeline` to correct peer and no forwarding will be done in `raw-pipeline` or `service-map-pipeline`.