document how to enable tracing

[butonic]

run jaeger all in one as per https://www.jaegertracing.io/docs/2.4/getting-started/

docker run --rm --name jaeger \
  -p 16686:16686 \
  -p 4317:4317 \
  -p 4318:4318 \
  -p 5778:5778 \
  -p 9411:9411 \
  jaegertracing/jaeger:2.4.0

set these env vars

          // tracing
          "OC_TRACING_ENABLED": "true",
          "OC_TRACING_TYPE": "otlp",
          "OC_TRACING_ENDPOINT": "localhost:4317",