[docs] Improve pipeline section docs

based on information provided: 
* https://docs.google.com/document/d/1NeheFG7DmcUYo_h2vLtNRlia9x5wOJMlV4QKEK05FhQ/edit?tab=t.0#heading=h.g6rvvz3l271i
* https://github.com/open-o11y/opentelemetry-collector-testing/blob/master/docs/design.md#receivers

Author: PadreSVK

content/en/docs/collector/configuration.md

@@ -638,6 +638,24 @@ service:
       processors: [batch, memory_limiter]
       exporters: [opencensus, zipkin]
 ```
+As with components, use the `type[/name]` syntax to create additional pipelines for a given type.
+
+```yaml
+service:
+  pipelines:
+    metrics:
+      receivers: [opencensus, prometheus]
+      processors: [batch]
+      exporters: [opencensus, prometheus]
+    traces:
+      receivers: [opencensus, jaeger]
+      processors: [batch, memory_limiter]
+      exporters: [opencensus, zipkin]
+    traces/better_pipeline:
+      receivers: [opencensus]
+      processors: [batch]
+      exporters: [zipkin]
+```
 
 ### Telemetry