Add "logs" as supported signal in the design doc (#5474)

docs/design.md

@@ -15,7 +15,7 @@ Data receiving, transformation and sending is done using Pipelines. The Collecto
 
 Pipeline defines a path the data follows in the Collector starting from reception, then further processing or modification and finally exiting the Collector via exporters.
 
-Pipelines can operate on 2 telemetry data types: traces and metrics. The data type is a property of the pipeline defined by its configuration. Receivers, exporters and processors used in a pipeline must support the particular data type otherwise `ErrDataTypeIsNotSupported` will be reported when the configuration is loaded. A pipeline can be depicted the following way:
+Pipelines can operate on 3 telemetry data types: traces, metrics and logs. The data type is a property of the pipeline defined by its configuration. Receivers, exporters and processors used in a pipeline must support the particular data type otherwise `ErrDataTypeIsNotSupported` will be reported when the configuration is loaded. A pipeline can be depicted the following way:
 
 ![Pipelines](images/design-pipelines.png)